You can split windows horizontally and vertically. You can have as many splits as you like.
Type :vsplit <path of file> to split the window in half vertically.
Type hsplit <path of file> to split the window in half horizontally.
You can navigate between the windows using the Ctrl+w sequence, followed by one of the movement keys (h, j, k, l).
You can change the layout of the windows after creation, too. First, navigate to the window you want to change. Then type Ctrl+wL to move it to the rightmost part of the window. To move it to the leftmost part of the window, type Ctrl+wJ. Top: Ctrl+wK, bottom: Ctrl+wH.
You can also resize windows by using the Ctrl+w+ and Ctrl+w- to increase and decrease the height of the current window respectively. To increase and decrease the width of the window, you type Ctrl+w> and Ctrl+w< respectively.
To make all the windows of equal width and height, you type Ctrl+w=.
To open a new tab in Vim, you type :tabedit <file path>.You can type gt to go forward, and gT to go backward. To close a tab, you can just type :q.