Good is an adjective. We use good when we want to give more information about a noun.

For example:

My dog Sam is very good. He’s a good dog.

She didn’t speak very good English. Her English isn’t very good.

Well is usually used as an adverb. We use well when we want to give more information about a verb.

For example:

He usually behaves very well.

She didn’t speak English very well.

Note! The exception to this can be when you talk about someone’s health:

For example:-

She wasn’t a well woman.

and when you describe sensations:

For example:-

This pizza tastes/smells/ looks good.

If you say “You look good.” It means they look attractive.

If you say “You look well.” It means they look healthy.

Note! Younger people might reply to the question “How are you?” with “I’m good.” This is what I call MTV English.

You may hear the saying “That’s all well and good.” It means something is basically ok, but with some shortcomings.