Breadcrumbs are the tiny bits of bread left after you cut a loaf, or the dry crumbs cooks use. In the kitchen they are pressed onto fish or chicken before frying, or scattered on a baked dish to make a crisp top. You can crush leftover bread yourself or buy a bag. Though actually, on websites the same word is used as a picture: the little trail of page names (Home > Kitchen > Bread), like crumbs dropped to find the way back. That computer use is only a metaphor; the real thing is still bits of bread.