Four Noble Truths
- There is suffering.
- There is a cause of suffering.
- There is an end to suffering.
- The way out is the eightfold path.
From Tricycle.org.
Disclaimer:
I'm only a Buddhist in that I consider it to have a lot of good advice.
If you want to know about the religion I'm probably not a great source unless you just want my opinions about it and my (secular) interpretation of some of the useful things it teaches.