Start by moving to "x" below and calling 'ma' on it.

  ----> x <----

This assigns the 'a' mark to that position.
Try typing 'a and `a and see what happens.

How about you assign another mark on "y" below.

  ----> y <----

Try flicking between the two marks. Edit some text,
add/remove some lines. Notice how the marks stay on x/y.

Now imagine there are far appart, and more than two.
How much better is that than scrolling!

Now make an edit somewhere and try `.
Isn't that nice :) `` / '' do something similar too.