This refers to the actors in a specific phrase.
I.e. Who is doing something in the phrase. In English you can have 1st person (I/me), 2nd person (you) , and 3rd person (he/she/it).
Person can also have gender (eg male and female) and number (eg singular for one person, dual for two people, trial for three people, and plural for more than three people.
Some languages also show differences when a (non-singular) person is inclusiveexclusive.
There are other possibilities, such as whether the ‘person’ is human or non-human, animate or inanimate, etc.
An English phrase such as “you see him” is ambiguous, as ‘you’ can be singular or plural, but this phrase can be parsed in the singular as 2sg – SEE – 3sg.