It allows you to lineup a block of text along a special character or piece of text.
A common use is in Makefiles or in long lists of assignments (as in C++ Constructors)
asdfasdsdf = hello hello = 1 j=1 asdsaffsd=29
turns into:
asdfasdsdf = hello
hello = 1 j=1 asdsaffsd=29
Often, this is considered to make things neater. Assignment is one place. By the way, I had to write my own version of this for SlickEdit since there isn't/wasn't one before.