Vitamins are organic chemicals which are substances that contain carbon, hydrogen and oxygen.
As you probably know, vitamins regulate a variety of bodily functions and are essential for building body tissues such as bones, skins, nerves and even blood.
They also help in digesting certain foods.
Your body needs many specific vitamins such as A, D, E, K, C, and the members of the B vitamin family which go from B1 to B12.
There are a few other vitamins or compounds that scientists believe to be beneficial beyond the previously mentioned ones which are the most well known.
Water and fat soluble vitamins A rule of thumb is that water soluble vitamins are much better because they don't have any side effects usually if taken in large quantities since excess vitamins will just be thrown away by your body when you urinate.
A good example of a water-soluble vitamin is vitamin C.
On the other hand there are fat-soluble vitamins which are, as the name implied, stored in body fat when not needed by the body.
These can become a bit more dangerous since they can actually have side effects since actually remain in your body.
For example an overdose of vitamin A can actually lead to liver damage, headaches, vision problems, sleep disorders and many others.
The side effects however only happen in large quantities and can only happen if you deliberately take many supplements in a specific vitamin.
Usually, if you simply eat foods in a diversified guide that should have all the vitamins it's almost impossible to have any overdose of a specific vitamin.
However I did mention vitamin A earlier and this is one of the only ones that it's actually possible to have an overdose from simply eating a lot of liver.
During the 20th century it actually made explorers in the South Pole very sick because they were constantly eating seal and whale liver which contains a toxic form of A in very large quantities.