There are many prefixes and suffixes in Japanese that are used depending on what the speaker wants to highlight.
ら is a suffix (component used after the main part of a word) that implies that there is ‘more than one’ of something. Due to this,
ら is often called a ‘pluralizing suffix’.
ら comes from the same kanji as
等（など）, and the literal meaning is closer to ‘(A) etc’.
This ‘etc’ is where the implication of ‘more than one’ originates. To use
ら, attach it to the end of any pronoun.
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彼（かれ）らは日本語（にほんご）を勉強（べんきょう）しにきた。
They came in order to study Japanese.
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お前（まえ）ら、アニメを見（み）ないの？
You guys don't watch anime?
Because ら has a literal meaning that is close to ‘(A) etc’, or ‘(A) and so on’, it may sometimes be considered a bit rude (due to being dismissive). Because of this, it is recommended to not use this suffix in relation to people, unless it is absolutely essential to indicate plural. In most cases, 達（たち） will be a far better choice.