Let's see... Argentinians use "Vos" instead of "tú" for the second person singular, so the conjugation of the verbs change.
Imperative of non-reflexive verbs...
tú - come
vos - comé (used in Argentina)
usted - coma (also used in Argentina - more formal)
nosotros - comamos
vosotros - comed (not used in Argentina)
ustedes - coman (used in Argentina)
tú - cuídate
vos - cuidate (no accent here) (used in Argentina)
usted - cuídese (also used in Argentina - more formal)
nosotros - cuidémosnos
vosotros - cuidaos (not used in Argentina)
ustedes - cuídense
you eat - tú come las manzanas
you eat - vos comé las manzanas (used in Argentina)
you eat - usted coma las manzanas
In this case, Usted is the formal form of the second person singular, meanwhile tú (vos in Argentina) is the familiar or more informal form we use to address to people you already know or young people.
You can address younger people with "tú" ("vos" in Argenitna) or some adult who is your age.
Usted is used when you address to your teachers or people who are older than you. Also when you first meet an adult. Conjugations for usted are the same as conjugations for él
lets eat - nosotros comamos las manzanas
you (plural) eat - vosotros comed las manzanas (not used in Argentina)
you (plural) eat - ustedes coman las manzanas (used in Argentina)
Hope it helps and I didn't confuse you more Just let me know please.