Net worth
Total value of all your assets at each moment in time. This includes spikes for deposits and drops for withdrawals.
Performance
A time-weighted return of your portfolio excluding withdrawals and deposits. This helps remove noise when you take actions like depositing money, selling an asset, etc. Learn more about time weighted returns here.
Learn by example
Henry has $100 in his portfolio invested entirely in Apple stock. He sells the entire position. Henry now still has $100 in his portfolio but as cash instead of stocks.
The net worth chart for the stocks page would show a 100% drop ($100 initially -> $0 now) while the performance chart would reflect a 0% change since he didn’t actually lose or gain any money. It’s now just sitting as cash.