This is the 60th most frequent Japanese word.
って
A casual particle used for quoting, emphasizing, or marking the topic in conversation.
Here, 'って' is used as a casual quoting particle, equivalent to 'that' in English, as in 'heard that...'.
彼が来るって聞いたよ。
I heard that he is coming.
In this sentence, 'って' highlights the topic informally, similar to saying 'Speaking of cats...'.
猫ってかわいいですね。
Cats are cute, aren't they?
Here, 'って' introduces a statement being questioned or referred back to, again as a quoting particle.