Private Equity_101

Hi,

I am new to private equity and am trying to grasp a couple of the concepts. would appreciate if you could help out.

1) How does a fund work? why is their multiple funds? can't you invest in another company if you still have money left from the fund?

2) I keep on seeing the word "equity check", what does that mean in the PE world

3) could you please describe what a shareholder loan is? what is the difference between the funds money?

4) what is funds of funds

5) what is a secondary fund

Thank you in advance