Let’s say when you invest in a fund with an NAV of 100.
After the first year, the NAV is 90, so you’re down 10%.
After the second year, the NAV is back up to 100, so that year you’re up 11%. However, the fund manager doesn’t get to take performance fees in the second year, because he/she lost money in the first year, and you’re no better off than when you started. They would only receive performance fees once the NAV goes above the point at which you initially invested (plus whatever the hurdle rate is).
Does that help?