Sometimes mild swelling and redness could occur, some chagnes in pigmintation and skin texture like scars but these effect are usually temporary effects.
You should precisely restrict to your doctor instruction such as sun protection especially if you had the procedure in your face or uncovered areas of your body.
If you had any tanning like tan sprays or tanning booths, you must wait till the tanning is faded, because it reduces the efficacy of the laser.
Laser targets only the active hair follicles, so it is necessary to have several treatments to have significant hair removal. And also the hair have a growth cycle so this hair removal treatment slow down hair growth but do not prevent it permanently, that is why you have to re-carry out the procedure periodically.