The MSB is the coarse part of the value of the parameter, while the LSB is the fine part of the value of the parameter.
As an example, CC 15 for the coarse part of the delay time and CC 47 is for fine adjustment of the delay time.
Yes. In the example of delay time, you could send CC 15 and it will cover the full range of possible delay times with coarse resolution. If you send CC 47 only, then it will make fine adjustments to the delay time in relation to the current coarse part of the delay time value.
(As an analogy, imagine separately changing the hours and minutes value of the time on a clock.)
There are some MIDI controllers that allow two CC messages to be combined so that you could use one physical control to sweep through the entire range of a parameter with fine resolution.