What do you mean, bed sign and bed sheet?
Fitted type is equivalent to the set on the mattress, sheets are directly laid on the bed.
The sheets are the most common general European style or colorful bedding for sheets, fitted type is generally styles commonly used abroad, because foreigners are lazy level in this area, convenient, a little difference in appearance and generally simple flower type or knitted fabric for.
The sheets are directly laid on the bed, surrounded by a natural sag, is fitted around the elastic band, a bed mat