SLANG WORDS
Slang is the use of informal words and expressions to describe an object or condition. Slang is vocabulary that is meant to be interpreted quickly but not necessarily literally, as slang words or terms are often a metaphor or an allegory.

Slang is sometimes regional in that it is used only in a particular territory. Slang terms are frequently particular to a certain subculture, such as musicians, and members of minority groups. Nevertheless, usage of slang expressions can spread outside their original arenas to become commonly used.

IDIOMS
An idiom is a combination of words that has a meaning that is different from the meanings of the individual words themselves. It can have a literal meaning in one situation and a different idiomatic meaning in another situation. It is a phrase which does not always follow the normal rules of meaning and grammar.
To sit on the fence can literally mean that one is sitting on a fence.
I sat on the fence and watched the game.
However, the idiomatic meaning of to sit on the fence is that one is not making a clear choice regarding some issue.
The politician sat on the fence and would not give his opinion about the tax issue.

Many idioms are similar to expressions in other languages and can be easy for a learner to understand. Other idioms come from older phrases which have changed over time.
To hold one's horses means to stop and wait patiently for someone or something. It comes from a time when people rode horses and would have to hold their horses while waiting for someone or something.
"Hold your horses," I said when my friend started to leave the store.

Other idioms come from such things as sports that are common in the United Kingdom or the United States and may require some special cultural knowledge to easily understand them.
To cover all of one's bases means to thoroughly prepare for or deal with a situation. It comes from the American game of baseball where you must cover or protect the bases.
I tried to cover all of my bases when I went to the job interview.

PROVERBS
A proverb (from the Latin proverbium) is a simple and concrete saying popularly known and repeated, which expresses a truth, based on common sense or the practical experience of humanity. They are often metaphorical. A proverb that describes a basic rule of conduct may also be known as a maxim. If a proverb is distinguished by particularly good phrasing, it may be known as an aphorism.

Proverbs are often borrowed from similar languages and cultures, and sometimes come down to the present through more than one language. Both the Bible (Book of Proverbs) and medieval Latin have played a considerable role in distributing proverbs across Europe, although almost every culture has examples of its own.