I think for the most part, the Goat nailed the distinction, but I'll add my bit more of understanding to it, as well as reiteration.
A Cover Band - tends to play top 40, and stay pretty faithful to the source.
A Cover Song - played by anyone, in any style, faithfulness to the original source (in terms of sound/structure) optional.
A Tribute Band - tends to play ONE ARTIST, and stay pretty faithful to the source (sometimes even so far as to dress like the band).
A Tribute Album - usually multiple artists paying homage to a musical style or specific band they grew up with or were influenced by, like cover song(s), faithfulness to original source material (sound/structure) optional.
At least that's how I understand it.