Wikipedia: Latin language/Conjugation

Conjugation is the creation of derived forms of a verb from one basic form. Conjugation may be affected by person, number, gender, tense, mood, voice, or some other language-specific factor or factors. When a verb is used to function as the action done by a subject, the verb must be conjugated in most languages.

For example, here's a sample conjugation of the English verb to be and its Latin and French equivalents, esse and être.

to be / esse / être
Form / Person	English	Latin	French
Infinitive	to be	esse	être
1st singular	I am	sum	je suis
2nd singular	you are	es	tu es
3rd singular	he, she, or it is	est	il/elle est
1st plural	we are	sumus	nous sommes
2nd plural	you are	estis	vous êtes
3rd plural	they are	sunt	ils/elles sont

Note that the similarity between English is and Latin est is not a mere coincidence, but rather one of the consequences of them having a distant common ancestor (see Indo-European languages). French is a derivative of Latin, which explains the much greater similarity in the way their conjugate this verb.