Semicolons are most often used to separate two related independent clauses. Semicolons are also used in lists that would confusing if the items were separated by commas. (Ex: I visited Huston, Texas; St. Louis, Missouri; and Spokane, Washington.)

The colon is used for mainly three things which are introducing a list of independent clauses, setting up a quotation, or defining or expanding an idea. Your sentence falls under defining or expanding an idea.

(edit fuck you gwahir for being faster to explain)

edit: just in case you're confused about terminology, "independent clause" is basically a simple complete sentence that can stand on it's own.