containing the mode
  prefix for which the mapping will take effect. The prefixes are the ones
  listed in |:map-modes|, or "!" for |:map!|, or empty string for |:map|.
• {lhs} is a string with the key sequences that should trigger the mapping.
• {rhs} is either a string with a Vim command or a Lua function that should
  be executed when the {lhs} is entered.
  An empty string is equivalent to |<Nop>|, which disables a key.

Examples:
>lua
    -- Normal mode mapping for Vim command
    vim.keymap.set('n', '<Leader>ex1', '<cmd>echo "Example 1"<cr>')
    -- Normal and Command-line mode mapping for Vim command
    vim.keymap.set({'n', 'c'}, '<Leader>ex2', '<cmd>echo "Example 2"<cr>')
    -- Normal mode mapping for Lua function
    vim.keymap.set('n', '<Leader>ex3', vim.treesitter.start)
    -- Normal mode mapping for Lua function with arguments
    vim.keymap.set('n', '<Leader>ex4', function() print('Example 4') end)
<
You can map functions from Lua modules via
>lua
    vim.keymap.set('n', '<Leader>pl1', require('plugin').action)
<
Note that this loads the plugin at the time the mapping is defined. If you
want to defer the loading to the time when the mapping is executed (as for
|autoload| functions), wrap it in `function() end`:
>lua
    vim.keymap.set('n', '<Leader>pl2', function() require('plugin').action() end)
<
The fourth, optional, argument is a table with keys that modify the behavior
of the mapping such as those from |:map-arguments|. The following are the most
useful options:
• `buffer`: If given, only set the mapping for the buffer with the specified
  number; `0` or `true` means the current buffer. >lua
    -- set mapping for the current buffer
    vim.keymap.set('n', '<Leader>pl1', require('plugin').action, { buffer = true })
    -- set mapping for the buffer number 4
    vim.keymap.set('n', '<Leader>pl1', require('plugin').action, { buffer = 4 })
<
• `silent`: If set to `true`, suppress output such as error messages. >lua
    vim.keymap.set('n', '<Leader>pl1', require('plugin').action, { silent = true })
<
• `expr`: If set to `true`, do not execute the {rhs} but use the return value
  as input. Special |keycodes| are converted automatically. For example, the following
  mapping replaces <down> with <c-n> in the popupmenu only: >lua
    vim.keymap.set('c', '<down>', function()
      if vim.fn.pumvisible() == 1 then return '<c-n>' end
      return '<down>'
    end, { expr = true })
<
• `desc`: A string that is shown when listing mappings with, e.g., |:map|.
  This is useful since Lua functions as {rhs} are otherwise only listed as
  `Lua: <number> <source file>:<line>`. Plugins should therefore always use this
  for mappings they create. >lua
    vim.keymap.set('n', '<Leader>pl1', require('plugin').action,
      { desc = 'Execute action from plugin' })
<
• `remap`: By default, all mappings are nonrecursive (i.e., |vim.keymap.set()|
  behaves like |:noremap|). If the {rhs} is itself a mapping that should be
  executed, set `remap = true`: >lua
    vim.keymap.set('n', '<Leader>ex1', '<cmd>echo "Example 1"<cr>')
    -- add a shorter mapping
    vim.keymap.set('n', 'e', '<Leader>ex1', { remap = true })
<
  Note: |<Plug>| mappings are always expanded even with the default `remap = false`: >lua
    vim.keymap.set('n', '[%', '<Plug>(MatchitNormalMultiBackward)')
<
------------------------------------------------------------------------------
Removing mappings                                       *lua-guide-mappings-del*

A specific mapping can be removed with |vim.keymap.del()|:
>lua
    vim.keymap.del('n', '<Leader>ex1')
    vim.keymap.del({'n', 'c'}, '<Leader>ex2', {buffer = true})
<
------------------------------------------------------------------------------
See also:
• `vim.api.`|nvim_get_keymap()|:     return all global mapping
• `vim.api.`|nvim_buf_get_keymap()|: return all mappings for buffer

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Autocommands