My mouth is very small. So I can only eat very tiny things like bacteria, fungi and protozoa which you couldn't see unless you are looking through a microscope. I also eat organic matter like plants (mmmm, salad) and decaying animals. I guess that sounds sort of yucky, but you humans eat dead animals and birds too.
Sometimes the bits of food are too big for my mouth, so I moisten them to make them soft and suck them right into my mouth. (Don't try this at home, human parents tend not to like this.)
Since I have no teeth, I cannot really chew my food like you do. I do have something inside of me close to my mouth called a gizzard. You might have heard this word before because birds, including chickens and turkeys, have a gizzard almost like mine. As I eat my food some grains of sand and soil get into my gizzard. These grains of sand and soil push against each other, mix with moisture and grind the food into tiny pieces (kind of like my own personal food processor).
When the food leaves my gizzard, it goes into my intestine. The food is dissolved there and absorbed into my blood. Then it is carried to all parts of my body to keep me strong, healthy and slimy.