Vim - reposition the view window

That is does - it keeps the cursor at current position, but moves the text in the screen

zz - positions the current line at mid-screen
zb - positions the current line at he bottom of the screen
zt - positions the current line at the top of the screen - same as z+<Enter>
:set scrolloff=3 - sets 3 lines of context for better scrolling (keeps the cursor line off the top/bottom of the screen)

H - move to highest visible line
M - move to middle visible line
L - move to lowest visible line