My French teacher said that est-ce que comes before a what question, but I'm confused on what it really means.
Can someone explain to me what it really means?
First, a correction: "est-ce que" comes before yes/no questions. "qu'est-ce que" or "qu'est-ce qui" (depending on if the "what" in the question is the object or subject, respectively) comes before what questions.
It's usually best not to try to directly equate phrasings of one language to phrasings of another. What "est-ce que" really "means" is that "what's about to follow is a yes/no question." It denotes yes/no questions and it's easiest, as a foreign language student, to just accept that fact instead of trying to seek reasoning where they may not be any. However, if you insist on a direct English translation, luckily "est-ce que" does fit into English's logical framework (albeit, rather unnaturally).
The direct, word-for-word translation of "est-ce que" would be "is it that". As one could imagine, it is perfectly correct to pose questions such as "is it that you are sick?". (Of course, native English speakers would probably never say that, although it is correct, and rather opt for "Are you sick?")