comer = to eat

yo como / nosotros comemos
I eat / we eat

tú (informal)comes / vosotros coméis
you eat / all of you (informal) eat

usted come / ustedes comen
you (formal) eat / all of you eat

él come / ellos comen
he eats / they eat

ella come / ellas comen
she eats / they (females) eat

This is called "conjugating" a verb. Many of the verbs that end in "er" follow this pattern. Take off the er ending, to get the stem (com) then add the ending that goes with the person who is doing the action. Example:

• primera persona, singular: Yo como muchas papas. = I eat a lot of potatoes.
  
• segunda persona, singular: ¿Tú comes carne?.= Do you eat meat ?
  
• primera persona, plural: Nosotros no comemos carne. = We don't eat meat.
  
• tercera persona singular: Rosa come mucho. Rosa eats a lot.
  
• tercera persona plural: Ana y Marta comen poco. Anne and Marta eat little.