How does $(......) work?

Hello,

Can someone plz explain and provide references to how $(....) works below and why we use it.

$mycred = Get-Credential

$CompName = Read-Host -Prompt "Enter Computer Name"

Write-Debug "user name: $($mycred.UserName)"

Write-Debug "password: $($mycred.GetNetworkCredential().Password)"

Thanks for your help! SdeDot