Refers to a physically small plate or dish, often used for side dishes, condiments, or individual servings.
Please pour soy sauce into the small dish.
I arranged the pickles on a small plate and served them.
Everyone took some food onto their small plates and ate.
I lined up several small plates on the table.
小皿 is a small individual plate, while 大皿 is a large serving platter shared by everyone at the table.
For flat dishes/plates, 皿 is the conventional counter; 枚 is also used for thin, flat items in some contexts.
Compound of 小 (small) and 皿 (plate/dish).