We use a comma (,) after the words yes and no when the begin a statement.
Yes, I would like to go to the movies.
No, I did not finish reading the book yet.
We use commas to seperate three or more words in a series.
I like to eat strawberries, blackberries, grapes, kiwis, and raspberries.
We use a comma before the word and, but, or or when two sentences are combined.
I like to play games, and eat snacks.
We wanted to go on a picnic today, but it started to rain really hard.
Do you like to bike in the summer, or swim?