them and us idiom informal
他们和我们;别人和自己人
used when describing disagreements or differences, especially between different social groups
If parents are encouraged to be involved in school, there is less chance of a them-and-us situation developing. 如果鼓励家长参与学校事务，家长和学校之间的矛盾就会小些。
The management has its own restaurant. - It's definitely a case of them and us. 高级职员有他们自己的食堂——这显然是一种划分员工等级的做法。