For mini marshmallows: does this mean the regular small marshmallows you can buy in a grocery store, or the super tiny (less than pea sized) marshmallows I saw in a candy-making section of a candy store?

it means the smaller ones in the grocery store.

I use any size marshmallows and it still works.

MM just means Marshmallow. You can use the big ones or the little ones (or even the flavored ones). As long as you are going to the total ounces or cups the recipe calls for you'll be ok.

it means... the ones on sale.... hehehehe

I also use large ones or mini ones.... they both work

hth