Can you explain when to use a semi colon and what is its purpose?

A semi colon is used to link 2 related clauses, before a conjunctive adverb or transitional phrase connecting 2 clauses, and separating items on a list that also contains commas

Explanation:

A semi colon "; " is a punctuation mark with 3 functions; it is used:

To link 2 complete and independent clauses that are related. Example: Kate loves attending ballet class; when she dances, she feels like a butterfly. Before a conjunctive adverb or transitional phrase that is connecting two complete and independent clauses. Example: Susan has never enjoyed playing sports; nevertheless, she never misses an NFL game on TV. To separate items in a list that also contains commas. Example: Children usually like eating ice cream with different topping combinations such as: caramel, nuts and chocolate chips; strawberries, marshmallows and pecans; and coconut, brownie bites and whipped cream.

When reading, semicolons indicate a pause moderately longer than that of a comma, but shorter than that of a period.