Depends on your filing status, but you get taxed a certain percent on the amount that falls into that bracket.
For a single filer,
$0 to $8,700 is taxed at 10%, so a max of $870.
$8,701 to $35,350 is taxed at 15%, so a max of $3,997.50 (plus the $870 from the previous bracket, $$4,867.50)...