Because I seem to be writing this over and over again.

Buddhism begins with the Four Noble Truths.

• Duhkha. This is commonly translated as suffering. To be alive is to suffer.
• Samudaya. The origin of dukkha is desire (craving, want, thirst, hunger, need, and so on and so forth).
• Nirvana. It's also known as Enlightenment. The end or cessation of dukkha. It's not heaven, as many believe, but a state where on does not suffer. You do not have to die to go to nirvana. You just have to understand.
• Magga. The path to nirvana is the Eightfold Path.

The Eightfold Path (in three categories).

Prajna or Wisdom

• Samma-Ditthi Complete or Right View
• Samma-Sankapa Complete or Right Intention/Emotion

Sila or Ethics

• Samma-Vaca Whole or Right Speech
• Samma-Kammanta Whole or Right Action
• Samma-Ajiva Proper or Right Livelihood

Samadhi or Mental Discipline

• Samma-Vayama Complete or Right Effort
• Samma-Sati Thorough or Right Mindfulness/Awareness
• Samma-Samadhi Integral, Holistic, or Right Concentration/One-Pointedness of Mind/Absorption/Meditation

There are the Five Precepts that essentially expound on ahimsa or do no harm.

• Refrain from taking the life of living beings. This includes all living beings, not just humans.
• Refrain from stealing.
• Refrain from engaging in sexual misconduct.
• Refrain from making false speech.
• Refrain from intoxicants, which lead to mindlessness.

Finally, there are the Three Jewels.

• Buddha: the ideal within all beings (not just the guy).
• Dharma: the teachings of Buddha (the guy, who is just a guy and not a deity).
• Sangha: the community or the people.

There is more doctrine, dogman, and or philosophy, of course, but these four things are the foundations of Buddhism, whatever the sect.