Feather pillows typically have a combination of down and feather filling. Down refers to the soft inner feathers of a duck or goose. Feathers are courser than down and less insulating. The difference between feather/down pillows vs. memory foam comes down to weight and feel.
Because feathers and down are much lighter than memory foams, down pillows feel fluffier and have a higher loft (height or thickness) without adding bulk. Down pillows don't have the same contouring support of memory foam pillows, but the higher the fill weight, the firmer and heavier the down pillow will be, which can offer more support for your head and neck.