What exactly is "exit" in Powershell?

Question

You can exit Powershell by typing exit. So far so good. But what exactly is this?

PS Home:\> gcm exit
Get-Command : The term 'exit' is not recognized as the name of a cmdlet, function, script file, or operable program. Ch
eck the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:4
+ gcm <<<<  exit
    + CategoryInfo          : ObjectNotFound: (exit:String) [Get-Command], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException,Microsoft.PowerShell.Commands.GetCommandCommand

So it's neither a cmdlet, function, script or program. Leaves the question what exactly it is.

This unfortunately also means that one can't create aliases to exit:

PS Home:\> New-Alias ^D exit
PS Home:\> ^D
Cannot resolve alias '♦' because it refers to term 'exit', which is not recognized as a cmdlet, function, operable prog
ram, or script file. Verify the term and try again.
At line:1 char:2
+ ♦ <<<<
    + CategoryInfo          : ObjectNotFound: (♦:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : AliasNotResolvedException

Are there any more such commands which are no commands?

ETA: Just for reference: I know I can simply wrap it into a function. My profile has the lines

# exit with Ctrl+D
iex "function $([char]4) { exit }"

in them. My question was just to know what exactly this command is.

Answer 1

Not the answer but you can do this:

PS> function exit {exit}
PS> set-alias quit exit
PS> quit

or even shorter:
function quit {exit}

Answer 2

I was going to say that it's a flow control statement, like if or return, but I searched the grammar and couldn't find it.

Answer 3

It's a reserved keyword (like return, filter, function, break).

Reference

Also, as per Section 7.6.4 of Bruce Payette's Powershell in Action:

But what happens when you want a script to exit from within a function defined in that script? ... To make this easier, Powershell has the exit keyword.

Of course, as other have pointed out, it's not hard to do what you want by wrapping exit in a function:

PS C:\> function ex{exit}
PS C:\> new-alias ^D ex

Answer 4

My question was just to know what exactly this command is.

Guess, this fact is known

PS C:\> man exit

NAME
    Exit-PSSession

# and so on