Firstly, sorry if im posting this in the wrong place.
Im currently doing my A2 Computing alevel, and on every paper a question on algorithms come up. I really dont understand them, for example this one:

MODULE XXX
Input numbers into a list
REPEAT
FOR index IN RANGE 1 to (list length -1) DO
IF list (index) < list (index +1) THEN
Interchange the contents of both elements
ENDIF
ENDFOR
UNTIL no interchanges
Output the contents of each element in the list
END MODULE XXX

Could someone please explain to me what each line actually means.
Also if anyone knows a way that i could learn how to understand these sort of algorithms, e.g. a website that teaches you this kind of stuff, could you please let me know about it.

Im really stressed out, cos these questions are worth usually around 8 marks and the total marks is 60. so please help!