Ego means "I"
Consumat means "he/she/it eats"
Consumo means "I eat"
Meum means "me" (technically it is the accusative form of I, but it means the same thing)
Cena means "dinner"
Cenam is the accusative form of dinner, which means that the action in the sentence is happening to it.

Anyway, ego wasn't necessary because saying "Ego consumo" like I did means "I I eat."
I just used it to make the example more obvious.