Why do our muscles get sore after a workout ?

I am often asked by newbies in the gym Why do our muscles get sore after a workout? and what are the best recovery tips? I try to simplify it and say rest and recuperate well from your workout. This is called DOMS I.e, delayed onset muscle soreness. This particularly happens in newbie because they are new to training and it's a new stimulas. It's seen the soreness is set in after a day or two and may be there for 3/4 days. I can say based on my personal experience that I get sore now even after so many years of training under my belt. However, not after every workout but after some of workouts. I train Heavy duty training and H.I.T high intensity training and I do get sore. Now how do we heal the soreness? Rest well Do proper warm up massage Get adequate sleep.