What is this EXPRESS slot in my laptop and what can he do?

vi
3

I have since 2007 a laptop, which mitlerweile with WIN 10 runs… Today I noticed on the right hand side, which is in my laptop sonschub where Express is on it… Can I tell you by accident what that is and what the good is? LG.

Su
Su
Ca

I always give everything. Not completely inexperienced. Never seen.