Learn Spanish (Spain): Voy a explicar brevemente lo que ha pasado. - I am going to explain briefly what has happened.

In Spanish, qué with an accent is a question word (like "What happened?"). Here, "what" doesn't ask a question; it means "that which" or "the thing that". For this, you need the relative pronoun lo que. You can't use just que because there's no specific noun earlier in the sentence for it to refer back to.

How does the formation of brevemente work?

Adverbs are formed by adding -mente to the feminine singular form of an adjective. Because the adjective breve (brief) ends in -e, it is the same for both masculine and feminine. Therefore, you simply attach -mente to get brevemente (briefly).

Why use the present perfect (ha pasado) instead of the simple past (pasó)?

In Spain, the present perfect (ha pasado) is preferred for actions that happened very recently or have a strong connection to the present moment. Since the speaker is about to explain the situation right now, the events feel immediate and highly relevant, making ha pasado the most natural choice.

Could I put brevemente at the very end of the sentence?

Yes, Voy a explicar lo que ha pasado brevemente is grammatically correct. However, placing the adverb immediately after the verb it modifies (explicar brevemente) is often preferred because it keeps the action and its description together before introducing the longer clause (lo que ha pasado).