We call these line power supplies that adorn our outlets wall-warts. They are also called Power-packs, Power adapters, Line adapters by others.
They are mostly low power levels up to about 25Watts and can have AC or DC voltages. There is no real standard for plug ends and it is important to get the right size - often notated by xxmm X xxmm where the first size is the barrel diameter and the next is the inside diameter. For DC supplies they can be either center-positive or center-negative.
Understanding our part numbersA part such as WW9D50P55-21 - reads :