acc assignment vs determination

hi,

1) acc assignment - can be in anywhere of various modules, fi, co, mm, fd. during data entry, we need to MANUALLY put in the gl account in acc assignment fields. right?

2) acc determination - define in obyc or vkoa. this will let the system to determine which transaction code like bsx, wrx to use depends on which business process. this is more to BACKEND defined as compare to account assignment. right?

3) what is the main difference of assignment and determination? can i say assignment only single gl account whereas determination will be the double entry.

hope to have clarification.

thanks