Subordinate clauses are dependent upon main clauses or other dependent clauses. They cannot stand on their own. Often they begin with words (subordinating conjunctions, relative pronouns or question words) that connect them to the independent clause. "weil" is one such conjunction that introduces a subordinate clause. So the dependent clause provides more information about the independent clause. Subordinate clauses that begin with "weil" (because) answer the question "Warum?" (why?).

Example:
Ich will den Job haben. — Warum?
Ich will den Job haben, weil ich Geld brauche.
(= I need money. That is why I want the job.)

Subordinate clauses with "weil" are always separated from the independent clause by a comma.