Is a comma necessary before conjunction and in a sentence?

As I had a doubt in English Grammar generally if we write a sentence to continue the statement we use comma as 'and' is used to combine the two sentences we called it as conjunctions conjunction words are like and, but, yet, For, Nor, or, so What my question is can we have a sentence with 'and' conjunction and preceded by a comma. Knowledgeable members, please respond to the question.