I really want to understand the answer to this question. Q: What is an exchange particle? A: A virtual particle that lets force act between particles in an interaction. This answer was given in my A-Level textbook but I can't for the life of me decode what it means. For example in beta minus decay (feynman diagram given below) the exchange particle is the W- boson. But how does the W- boson let force act between the particles in this interaction. I would be grateful for any response but please bear in mind that I am an A-Level physics student (british high school) so am likely not to understand anything too complicated. Thanks!