Learn Italian: Il relatore, il quale ha presentato il progetto, è un esperto. - The speaker, who presented the project, is an expert.

In this sentence, you could absolutely use che. However, il quale is a more formal, stylistic alternative. It is highly common in written Italian, journalism, and formal speech. Because it changes to match gender and number, it completely removes any ambiguity about who the subject is in more complex sentences.

How do I know whether to use il quale, la quale, i quali, or le quali?

The relative pronoun must agree in gender and number with the noun it refers back to (its antecedent). Here, it refers back to il relatore, which is a masculine singular noun, so we use il quale. If the speaker were female (la relatrice), it would become la quale.

Why are there commas around il quale ha presentato il progetto?

The commas show that this is a non-defining clause—it adds extra, descriptive information about the speaker, rather than singling out which specific speaker we are talking about. Italian writers frequently prefer il quale over che in these parenthetical, descriptive clauses to elevate the style of the sentence.

I've heard the word relatore in a university context. Does it mean something different there?