Generally, it means that the seller would like to sell the house quickly at a reasonable price so they can move on with their lives.  It does NOT mean that any lowball offer will be entertained or accepted.  It does NOT mean that the seller will pay all closing costs.  But it does mean that a reasonble offer will be considered.  The seller may be maintaining 2 households and that could be the motivation.  Your Realtor may be able to shed more light on any particular property with that commentary.

You should consider putting yourself in the place of the seller to more fully understand the reasons for motivation.  You can pick up a gem of a home in this situation at a good price.  But you shouldn't expect to steal it.  A home inspection is a must, as in some instances, a growing proprety problem could be the motivation.