Confused with -Include parameter of the Get-ChildItem cmdlet

You're confusing the use of -include. The -include flag is applied to the path, not the contents of the path. Without the use of the recursive flag, the only path that is in question is the path you specify. This is why the last example you gave works, the path c:\test has a t in the path and hence matches "*t".

You can verify this by trying the following

gci -path "c:\test" -in *e*

This will still produce all of the children in the directory yet it matches none of their names.

The reason that -include is more effective with the recurse parameter is that you end up applying the wildcard against every path in the hierarchy.

Try the -filter parameter (it has support for only one extension):

dir -filter *.txt

Tacking on to JaredPar's answer, in order to do pattern matching with Get-ChildItem, you can use common shell wildcards.

For example:

get-childitem "c:\test\t?st.txt"

where the "?" is a wildcard matching any one character or

get-childitem "c:\test\*.txt"

which will match any file name ending in ".txt".

This should get you the "simpler" behavior you were looking for.