Wikipedia's rules and best practices are specified in two types of documents:
Policy
A policy documents a rule or standard with wide acceptance among Wikipedia editors that all users should normally follow.
Guideline
A guideline is a set of best practices that are supported by the consensus of Wikipedia editors. Editors should attempt to follow guidelines, though they are best treated with common sense. Occasional exceptions may apply. Naming conventions are considered guidelines.
The basics
The Five Pillars
The Five Pillars are the five fundamental principles of Wikipedia:
Visit the Teahouse if you are a new editor looking for interactive help, or the Help desk for an interactive Q & A forum Ask for help on your talk page