Use a semicolon to show a link between two clauses. This should not be used if it makes a sentence over 25 words.

It is used to show that the second clause of a sentence is dependent on the first – that there is a link between them.

Each person is different; it is what makes life exciting

The fact that each person is different is the thing that makes life exciting. There is nothing else that can make life exciting in this situation, apart from each person being different. The ideas before and after the semicolon must be full sentences that could stand alone if necessary. If not, a semicolon must not be used.

Each person is different
It is what makes life exciting