It's an informal expression, so it's best used in casual conversations, not in formal writing or speeches.

Informal Usage

This phrase is considered American slang, so it may not be well understood outside the United States.

American Slang

The phrase alludes to Mexican food but has no relation to Mexican culture when used in this context.

It’s used to emphasize the major or crucial aspect of a problem or situation.

Usually indicates a challenge or obstacle that is significant and potentially hard to overcome.

When mentioned, this phrase often signifies where most of the effort or attention is needed.