Smart Playlists in iTunes are lists of songs that automatically update according to search criteria. You can create a Smart Playlist that looks for songs in your library according to how recently they were added or played, or how you have rated them, their genres an other properties.
With "My Queue" you can quickly save videos to watch later.
To add an item to your queue just click the sign next to the video.
Once you've added a video visit "My Queue" to start watching!