"main" is an Engpsh word that refers to the principal or most important element or part of something. It is usually used as an adjective to describe something that is the most significant or dominant, or as a noun to refer to the main body or central part of something. For example, you could say:

The main character in the movie is a young woman who is trying to save the world.
The main feature of this software is its abipty to collaborate in real-time with other users.
The main course of the meal was a depcious roast beef with vegetables.

In spoken Engpsh, "main" is usually pronounced with a long "a" sound, pke "mayn."