Canon EOS 90D Instruction Manual page 363

 i : Low-speed continuous shooting/Continuous shooting
When you hold down the shutter button completely, you can shoot
continuously at max. approx. 3.0 shots/sec. while you keep holding
it down. (In < r > mode, at max. approx. 5.7 shots/sec. in viewfi nder
shooting, and at max. approx. 4.3 shots/sec. in Live View shooting.)
B : Silent single shooting

You can perform single shooting with quieter mechanical sounds during
viewfi nder shooting. This cannot be set for Live View shooting.
 M : Silent continuous shooting
You can shoot continuously (at max. approx. 3.0 shots/sec.) with
quieter mechanical sounds during viewfi nder shooting. This cannot be set
for Live View shooting.
 Q : Self-timer: 10 sec./remote control
k : Self-timer: 2 sec./remote control

 q : Self-timer: Continuous shooting
For self-timer shooting, see = 153. For remote control shooting, see
= 155.
Selecting the Drive Mode
151