There is no single, standard answer to this question. Different individuals might turn to meditation for different reasons. Some of the 'answers' are given below. Probably one of these might be the answer for you.
To find peace of mind:
Currently we have a lot of mental problems. Because of those problems we lose the calm or peace of mind in our daily life. We have been trying to solve them desperately for a long time. But we have not been able to solve it till now. We sought the help of priests, gurus, psychotherapists, friends etc, still we don't think that we have solved them in its entirety. Then we decide to try meditation to solve our problems. Surely meditation is not a magic wand, by waving which we are going to solve all our problems right now! But it can help us to look our life in a different light, a better or higher perspective, in which the problems may be less severe or may wane to oblivion. Meditation will surely help us to understand more about ourselves, our mental states, desires, emotions etc. With this understanding we will be able to face the problems of life in better light.
To understand the mind/ To control the mind/ To transcend the mind/ To explore the inner life:
We have learnt so much about our body, matter and the world around us, but we know almost nothing about our mind or being. Let us put aside what all those philosophers are trying to put into our head. Do we know ourselves? Do we know our mind?
Our mind is a bundle of thoughts. We keeping thinking, thinking.... all the time. Is thinking a faculty of mind available to us? Or are we thinking obsessively? As of now, it looks we are thinking obsessively. At times we find it difficult to fix our mind on a single object even for a few seconds. Mind starts to wander all by itself, even thought we want to fix it on a particular object.
Is our thinking rational and coherent? Probably not. If we watch the thoughts that rise within us for a few minutes, we see that most of them are unconnected and irrelevant. If our thinking is so incoherent and purposeless, how are we going to solve our problems with this state of mind? A confused mind probably cannot find a clear solution for the problems of our life, isn't it? Planning is good, but most of the time our thinking is not coherent and useful.
Then, is there some other state beyond this confused, obsessive thinking ? Yes, within this analytical core of our mind, there is an intuitive core. Our whole education system only emphasises analytical thinking and not the intuitive thinking. But remember all creativity, born in the form of sudden flashes, are from the intuitive mind. All creative works are born out of the intuitive mind and not the analytical mind. We have to learn to tap the source of intuitive wisdom within us, which is always available, wise and loving. To make contact with our inner self, the intuitive mind, we have to slow down the analytical thinking. And when we make deeper and deeper contact, the inner mind will start guiding/ healing our external life. This is the aim of any meditation practice. For doing this we need not believe in any god or religion or philosophy. We just need to understand ourselves, our being, our intuitive mind.
Say, one very bad day you are put inside a dense, wild, haunted forest, inside which you are told that many wild animals and deadly ghosts are prowling around and that you have to live for the rest of your life inside it. It is a very dense forest, you don't know from which bush an animal or ghost might pounce on you! But luckily, there are sufficient fruits and roots and fresh water sources inside. But you are alone and forever inside this forest.... What you should be doing first? The first thing we should do is make a CLEARING, where we can live safely, so that we can see the any wild animal when it is approaching us.
The above mentioned dense, wild, haunted forest is our own mind. It is dense, wild and haunted due to the continuous proliferation of forceful, assertive, violent, painful thoughts. We have to live with it forever. And inside it there is no one else, we are all alone inside it...We have to create a 'clearing' within us by clearing or slowing down thoughts and opening to the intuitive wisdom within us.
Touching or reaching the inner or intuitive mind is the transcendence of the analytical mind. This is understanding the mind or mind-control.
To find happiness or joy:
Everyone is searching for joy, knowingly or unknowingly. But no one seems to have got it for sure. Why? Probably we are searching in the wrong place. If we left our keys at home, what is the use is searching it at the office? All of us are searching for joy in the external world. Are we searching in the wrong direction? Is there joy in the inner world?
Probably there is joy within and not without. The best example is deep sleep or dreamless sleep state. Whether we are tired or sad or sick, we feel refreshed by deep sleep. Our mind and body gets refreshed by deep dreamless sleep. This shows that there is a process within us, by which we can refresh ourselves all by ourselves, without the mediation of gods, priests, religion, philosophy. The existence of such a mode of refreshment implies that there is a inner source of joy within us. Can we gain that refreshment or joy consciously?
Again, if our sleep was filled with dream, we get up unrefreshed. Why? Dream is also a form of thinking, semi-conscious thinking or cud-chewing of past-impressions. And this thinking makes us tired. This also shows that we can access joy or happiness without the faculty of thinking.
In dream we might have a dream body/personality which is different from
our 'real' or daily body / personality.
In deep sleep even that gets dropped. In deep sleep, when the possession
of mind and body itself is not tangible, the other objects of possession
like wealth, education, status etc. are non-existent. Thus in deep sleep
we are able to enjoy happiness without possessing any object! But in daily
life we believe that we have to run behind objects to get happiness. Can
we tap this inner joy consciously? Yes, meditation can help us to get in
touch with that inner source of joy.
To find a higher purpose of life:
We are born, we get educated, we get a job, we marry and we make our own family, we educate our children, we help them to get a job, we get them married to a suitable person, we help them build their own family, we get old... and one day we have to die. This is the best scheme of life which we can imagine. Is that all there is in life? Is there nothing beyond this common daily life? Am I born to live and die like this?
For some, this question motivates them to look inside, to look into the purpose of their existence. For that inner search meditation is the tool.