A semi-colon works the same as a comma and a conjunction in a Compound Sentence.

It is meant to signal a pause in the sentence that is longer than a period but shorter than a comma.

Hint: A semicolon looks like a period placed above a comma, since it signals a pause in length between comma and period.

Example:

Compound Sentence with comma/ conjunction

We will go to the park, and Bill will play in the fountain.

Compound Sentence with semicolon

We will go the the park; Bill will play in the fountain.