To get the list of all the variables or functions that have been declared and pre-existing:
Note: You can change the wildcard(*) if you are looking for something more specific.
ls can obviously be substituted with dir or get-childitem if you are more familiar with those key-words.
If you want to look more closely at what the function is actually doing then you just need to type: $function:<name of function> like so:
which will return:
param([string] $name) New-Item $name -type directory