How to comapare two folders and copy differrent files in many locations

I need the following ( in powershell )

1- to compare two folders on the following basis

          if file does not exist  ( means new file )

          if file exist but had different date or length  ( means modified file )

2- Capture above files (i.e. differences ) and copy it to 2 or 3 locations

I saw many items in the internet compares existing files and stopping on that stage.

Thanks in advance