A question word plus -(으)ㄴ지 makes an embedded question, and 알리다 — nearly always 알려주다 or 알려드리다 here — is handing the answer over. It is the standard shape for the promise a video makes to its viewer: 그게 뭔지 알려드릴게요 (I'll tell you what that is), 김천이 왜 '김밥천국'인지 알려드립니다. The one line with bare 알리다 is about making a fact known to people at large rather than to one listener.
Register: neutral to polite; common in explainer video