Machines are good for people who want to get in and out of the gym as quickly as possible but yet get an effective workout. Not only do some machine exercises work things that free weights can't, you also need them even if you are a free weights user. The lat pull down works your lats better then anything else. Leg curls hit your hamstrings better then anything else and the leg extension helps build definition in your quadricepts.
They are also the safest way to work out because unlike free weights if you feel like something is going wrong, you can just let go and lower the weight. However machines don't exactly give you the pump that free weights do. Yeah, you can lift more with a machine but you can't get as good of a workout.
Free weights are the greatest way to build muscle. For example with machines you can only do a chest press at one position but using free weights you can work all three parts of your chest with flat, incline, and decline bench. If you want to workout your back you can to bent barbell rows, deadlifts, and bent one arm dumbell rows which works out all of the vital areas of the back. Also with free weights it gives you a better pump then what you get with machines which is very important for gaining mass.
However free weights are more dangerous then machines, but if you lift smartly you shouldn't get hurt. Well that tells you what you need to know about both see ya next time.