When should I use mineral supplements!

Hello. I'm 22 year old female and I'm student of international law, second year. Just the other day I was confused with one thing and I would like if someone could clear this up for me.
You see, about a week ago I started to feel almost constant tiredness and pain in muscles. Although I was sure I will develop flu or something- I didn’t. I was perfectly healthy, but I felt exhausted!
I talked about it with a good friend and he told me that it is quite common problem for him and that he, in these cases, take some mineral supplements and that’s all. Can someone tell me more about these supplements?

Hello. I know that all this about mineral and vitamin supplements can act confusing on people- it is very simple. I also didn’t know what is the best timing for usage of these supplements, how can they help me and can they substitute any kind of food!
The thing is that our body only needs a small amount of vitamins every day but these supplements are especially good for pregnant women, women who are breastfeeding, people who drink alcohol, cigarette smokers etc.
You should also know that they shouldn’t be used as substitute for some nutritious diet! In most cases- they really can help your general health state! But still- it is best to get vitamins from eating a varied diet.