In general, people always abide by the principle of "birds of a feather flock together" in real life.
In general, in real life, people often adhere to the principle of "clustering things by class".
Historical allusions
It originated in the mid-16th century. "feather" means "feather" and "flock" means "gathered". The slang literally means "birds with the same feathers come together". It is similar to the Chinese"things are clustered, people are divided into groups; a hill of raccoons" and so on.

dialogue
Rose:
Tom threw me on the highway yesterday.
Tom threw me off the highway yesterday.
Kevin:
Never to play with Tom again! He is such a bad guy.
Don't play with Tom anymore, he's a bad boy.
Birds of a feather flock together. He is not my friend any more.
Things are clustered in groups, and people are grouped. He's no longer my friend.
Single word
flock
[flɔk]
n. Swarms
feather
['feðə]
n. Feathers
highway
['haiwei]
n. Highways, main roads