Tab: default behavior of vim is: add &tabstop spaces unless expandtab is not set. You can always insert real tabs by <c-v><tab>. However tabstob should be treated as display setting. Use sw setting and c-t, c-d instead.
c-t: increase indentation c-d: decrease indentation c-f: auto indent current line (requires indentation setup) :setlocal sw=4: use 4 spacse for indentation :setlocal expandtab: expand tab to spaces (default) :setlocal tabstop: a tab is viewed as how many spaces in a file? :set list : displays spaces and tabs
Where to set those options?: See configuring-vim
The :h = is the command which is commonly used for using the Vim's indentation features. Some use cases:
gg=G: reindent whole file >3j . . increase indentation of 3 lines and repeat two times V/ABC<cr>= :select everything till ABC then reindent this block