Francescatotty

I agree with all the other people up there ^^, For example: I laid my head on his shoulder. ( past tense )

I lay my head on his shoulder. ( present tense )

With commas you use them for lists etc:

Dog, Cat, Wolf, Fox.

You also use them for pauses to make it * a greater effect * etc:

I was walking along then I saw it, (pause) ....

Also in some cases it is used instead of ands!

Etc:

I hope this is helpful, good luck learning it!