N4
～ら
We, Them, They, These, Those
彼らは日本語を勉強しにきた。
They came in order to study Japanese.
Explanation
「〜ら」 attaches to a pronoun or a noun for people and makes it plural. It is casual and spoken, used for yourself, peers, younger people, or things:
1Personal pronouns: 僕ら (we, men's speech), 彼ら (they), 君ら (you all), あいつら (those guys, very casual).
2Demonstratives: これら (these), それら (those), あれら (those over there).
Mixed up with
The three plural suffixes, from most to least respectful:
「〜がた（方）」: the most respectful: 先生方, 皆様方.
「〜たち（達）」: neutral, the everyday choice: 私たち, 子供たち, 山田さんたち.
「〜ら（等）」: casual, no respect: 僕ら, 彼ら, あいつら.
「〜ら」 shows very little respect, so never attach it to a teacher, boss or customer: not 「先生ら」 or 「お客様ら」.
For plural things, only 「これら」, 「それら」 and 「あれら」 work, not 「これたち」.