Thank you for the opportunity to help you with your question!
WAR tries to represent a general statistics worthness of a player in all aspects. Players contribution towards the team can be calculated with several questions asked and answered as winning points. I.e if player X going on retirement, how posible is it to replace him, economic wise?...then the value could be translated as wins..I.e +8.5 (player x),+ 3.6(player y)
Please let me know if you need any clarification. I'm always happy to answer your questions.