Your first example uses the “Name” positional parameter:
[pre] get-alias ls
[/pre]
Which is the same as:
[pre] Get-Alias -Name ls
[/pre]
With the second example you provided, you need to use a different parameter set. You want to use the “Definition” parameter and it’s not positional so it can’t be omitted:
[pre] Get-Alias -Definition Get-ChildItem
[/pre]
Same thing with the third example:
[pre] gal -Definition Set-Alias
[/pre]
Here’s all you need for the forth example:
[pre] gal sal
[/pre]
Take a look at the full help for Get-Alias and I think all of this will become self-evident.
[pre] help Get-Alias -Full
[/pre]