1) There are lots of formal explanations.
2) But, let's make the concept easy . . .
3) Picture yourself at home
. . . waitress (aka, Mom) sets the table
. . . she then sets the food on the table in serving dishes
. . . the family then grabs and shoves to get their choice
. . . they continue to grab and eat until full
. . . sometimes manners count, sometimes they don't
. . .when done, everyone gets up and leaves the table a mess
4) Same thing at LTT, except Mom is one of the diners, not the waitress