Learn Spanish (Latin America): El delegado, el cual es de México, redactó el documento. - The delegate, who is from Mexico, drafted the document.

You can actually use quien or que here! El cual (meaning "who" or "which") is simply a more formal option, often used in written Spanish, the news, or formal speeches. It is especially common in clauses surrounded by commas that add extra, descriptive information.

How do I know whether to use el cual, la cual, or lo cual?

These formal relative pronouns must agree in gender and number with the specific noun they refer back to. Because it refers to el delegado (a masculine, singular noun), it has to be el cual. If the subject were la delegada, it would be la cual. (Note: lo cual is used to refer back to a whole idea or situation, rather than a specific noun).

Do I have to include the commas around el cual es de México?

Yes, in this specific sentence you do. The commas show that his origin is extra, bonus information (a non-defining clause). When el cual and its forms are used without a preposition in front of them (like en or para), they are almost always kept inside these comma-separated phrases.

Wait, does redactó mean he censored or blacked out the document?