shutter speed in digital camera like dslr is fixed, they work by capturing the image > store to onboard buffer > store to memory card

but higher speed memory card allow to you to be ready for the next round of shooing in shorter time


dslr got a mirror which reflect the light to viewfinder, and a shutter curtain which open up to let the light hit the sensor for certain amount of time, all of this is electronic controlled mechanical that's why you will hear the "click" sound from the mirror when the button is pressed

and the dslr sensor is not on all the time unlike what you see in most compact pns and handphone camera
shutter lag - the difference between the time when you pressed the shutter button and the time where the camera is actually taking image

shutter speed - the interval of the shutter curtain remain open to allow light hitting the sensor

shutter burst/burst shot - mirror and shutter continuously open at a fixed interval to allow multiple pictures to be taken

shutter lag can be caused by the AF system in the camera, which is why camera has two stage shutter button, half-pressed shutter will auto focus and full-pressed from half-pressed will capture the image to reduce the shutter lag, manual focus also can reduce shutter lag since the camera no need to focus before user pressed the shutter button