Delayed Onset Muscle Soreness or "DOMS" for short is the soreness and ache in a muscle after exercise. This can happen anywhere between 24 hours to 36 hours after exercise.

Most beginners will get DOMS because the muscle fibres are not used to tearing and being put under tension and stress. This means that the next day that muscle group will feel particularly tender when touched or when stretched. For people who are used to going to the gym DOMS may not happen as often or at all.

This DOES NOT mean you're not training hard enough despite what people think. A lot of factors can affect how bad a person has DOMS. Recovery being the key factor. If your nutrition has been set and you are getting adequate amount of protein and carbohydrates around your training then you should be able to recover better with time.

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 DOMS are actually a very good way to see if your training your muscles correctly. For example if you are doing Lat Raises, then your shoulders should ache after, and the next day/day after you should (maybe) have DOMS through your shoulders.

However - if your shrugging your shoulders up when executing Lat Raises and the next day your Traps are sore then that means your dominating through your Traps and not your shoulders.

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 DOMS are not bad if you get them and if you don't. However it is recommended to switch up your exercises every 8-12 weeks depending on your experience in a gym. Try different styles, exercises, handles and attachments with equipment to target more of the muscle group your trying to work.