What does TCP/IP, OSI model even in means in job requirements

I've seen many jobs with one of these terms in description
Familiarity with OSI model, TCP/IP

I'm a dumb self taught guy. I know some advanced things but sometimes have no clue about very minute/basic things.

I'm aware what OSI model , TCP/IP is.

But why do job have it mentioned in their description, what practical use does this serve on the job ??

cybersecurity job requirements tcp