Can somebody explain this stuff about relative vs absolute addressing ?

Also, if I'm on a sub-sub-folder and want to address something that is on the same level (sub-sub) but on ANOTHER folder, I have to go back one step (sub) and THEN go to the other folder, right ?

Doing sub1/sub2/folder1 and then sub1/sub2/folder2 doesn't work.

"../" is troublesome and send me back (most but not all the times) to the TOP (root) level.

So my question is : is there an instruction like the ol' "cd.." of MSDos fame to back-up ONE level at a time ?