Person vs. number
When we speak, there are three kinds of roles being played: someone speaking, someone being spoken to, and someone or something else being spoken of. For example, "I (first person) told you (second person) that Chris (third person) went to the store."
Grammatical person is the generic term for those roles.
The first person is the speaker.
The second person is the one being spoken to.
The third person is someone or something else being spoken of.
The word "person" comes from Latin persona, meaning a role in a play. This meaning is retained today in the phrase dramatis personae.
Grammatical number is a different concept, meaning the number of people or things being referred to, usually distinguished in Latin (and English) grammar as singular or plural.
The verb in Latin (and English) is said to "agree in person and number" with its subject. That is, the form of the verb varies according to the grammatical person of its subject and according to the grammatical number of whatever is playing that role.
In English, the plural is the same in all three persons, and our second-person pronoun you is grammatically plural even though we use it to stand for one person. We still retain an archaic second-person singular pronoun thou, which takes its own verb ending: -est. In the first person, our verbs also don't distinguish singular and plural. Hence:
First person: "I go," "We go."
Second person: "Thou goest," "You go."
Third person: "Chris goes," "They go."
In English, the plural form of the verb is also the same as the infinitive and imperative. Infinitive: "It's time to go", "Let him go." Imperative: "Go!" The rare subjunctive mood is also the same: "I require that Chris go."
In the past tense and with modal verbs (will, can, must, should, etc.), we do not modify the verb at all to reflect the person or number of the subject. Hence "I went," "we went", "you went", "Chris went", "they went" (But "thou went'st.")
In Latin, all six combinations of person and number are distinguished in the form of the verb.
First person: "Ego eō," "Nōs īmus."
Second person: "Tū īs," "Vōs ītis."
Third person: "Chrīstophorus it," "Illī eunt."
The Latin infinitive and imperative are also distinguished: "Īre"; "Ī," Īte."
And in Latin, the six combinations of person and number are distinguished in all tenses and moods:
First person perfect: "Ego īvī," "Nōs iimus."
Second person perfect: "Tū īstī," "Vōs īstis."
Third person perfect: "Chrīstophorus īvit," "Illī iērunt."
In Latin, since the verb indicates the grammatical person so clearly, subject pronouns are usually omitted.