Surprise! You have been using buffers all this time. A "buffer" is just "a file in memory"; if you have 1 split on your screen, with a different file in each split, then you are viewing 2 buffers.
The two things which will probably give you the biggest bang for your buck are:
:ls
Which lists all buffers currently in memory, and:
:b
Which supports tab completion, allowing you to instantly jump to any file with just a few keystrokes. You'll also probably enjoy Ctrl + 6 / Ctrl + ^, which swaps between two buffers.
You'll need to do
:set hidden
before switching between buffers in a single window. Don't worry, though; if you try to quit without saving a modified buffer, or use :bd to delete a buffer without saving it, vim will yell at you.
<leader>b is a good replacement for both :ls and :b if you're using Command-T (like grandparent is). I was surprised when I discovered that feature, since it isn't quite as advertised/popular as the file opening capabilities of Command-T
BufferExplorer is a good plugin to have around. <leader>be will give you a listing of all of your buffers and allow you to do things like hit 'd' to delete the buffer under the cursor.
The two things which will probably give you the biggest bang for your buck are:
Which lists all buffers currently in memory, and: Which supports tab completion, allowing you to instantly jump to any file with just a few keystrokes. You'll also probably enjoy Ctrl + 6 / Ctrl + ^, which swaps between two buffers.You'll need to do
before switching between buffers in a single window. Don't worry, though; if you try to quit without saving a modified buffer, or use :bd to delete a buffer without saving it, vim will yell at you.