What's “ to gain exposure to sth"meaning

I read The cfa books . It said
Home or auto purchase have been traditionally financed by loans originated by financial institutions . for investors to gain exposure to these relatively iliquid loan, they must hold some combination of desposits,debt or common equity issued by banks.
So, what I cann’t understand is why investor must hold debt or common equity when they have home or auto loans. And “ to gain exposure to something” that something to investors is good thing or bad thing.
I expect your opinion.