Understanding windows in Vim

I have an understanding of buffers, but I am unsure as to how to navigate through windows? I use the Ack plugin and NERDTree. If I search for something in Ack while having both the NERDTree window and my main coding window open, how can I switch between these three different windows?

Occasionally, I accidentally open a file that takes over the NERDTree window, so now I have two windows with code, and one Ack window. Then I have to end up开发者_StackOverflow社区 closing the buffer I opened, which ends up closing the window, then reopening NERDTree.

You can move between windows by doing the following: Ctrl-w followed by a directional key, for example h, j, k, or l (or by using the correspondingarrow keys).

If you manage to open another buffer in the current window you can use C-i and C-o to move backwards and forwards in your jump list which should bring you back to your nerdTree buffer I believe (dont use nerdTree myself so can confirmit)