is there a max on size of contacts

[53Norwood]

I have loads of contacts and I wonder whether I need to buy ACT- It seems
like there is a limit on the space for contacts as one of them kept goin
ginto accounts - also is there a way to have contacts be the first one you
see to select from-
I don't understand accounts, business contacts and contacts
Is there a location that explains this-vs. ACT?

Thanks.
Peggy