This program multiplies integer inputs A and B, by repeatedly adding B to RESULT while decrementing A.
It will work fine when either A or B is zero. If A is zero, it will branch to QUIT immediately. If B is zero, zero will be added repeatedly to the result (which also is initialized with zero).
LOOP, RESULT etc. are called labels. They translate into a memory address location of a variable or machine instruction. But it is much more readable to have them as english words while creating your program. Also, they make your program relocatable, in the sense that while writing, you don't have to decide on which physical address your program will run.