For the present tense:
* "Être" (to be) is the verb for "are" when it's used as a linking verb.
* Example: "They are happy." -> "Ils sont heureux."
* "Avoir" (to have) is used with some verbs that are conjugated with "avoir" in French, like "to be hungry" or "to be thirsty."
* Example: "They are hungry." -> "Ils ont faim."
For other tenses:
* "Était" (was/were) for the imperfect tense.
* Example: "They were happy." -> "Ils étaient heureux."
* "Étaient" (were) for the plural form of "était" in the imperfect tense.
* Example: "They were happy." -> "Ils étaient heureux."
* "Seront" (will be) for the future tense.
* Example: "They will be happy." -> "Ils seront heureux."
* "Ont été" (have been) for the passé composé tense.
* Example: "They have been happy." -> "Ils ont été heureux."
Remember that the conjugation of "être" and "avoir" changes depending on the subject pronoun (I, you, he, she, it, we, they).
Here is a table of the conjugations of "être" and "avoir" in the present tense:
| Subject | "Être" | "Avoir" |
|---|---|---|
| Je | suis | ai |
| Tu | es | as |
| Il/Elle/On | est | a |
| Nous | sommes | avons |
| Vous | êtes | avez |
| Ils/Elles | sont | ont |
For more detailed information on conjugations and different verb tenses, please consult a French grammar textbook or a reliable online resource.