It means the files are not being shared. To share then again, select them via Control-click & you have option to share again. Likewise for folders.

The incomplete folder is a little different. If you are partial file sharing (sharing what % you have downloaded) then they will be black, otherwise red (partial files sharing can be set in preferences). Another reason incomplete files can be red is if there's been a corruption of the download list & LW has forgotten them.