An acute accent is a little mark that you can see above some letters. It looks like a tiny stick leaning to one side. When you put it over a letter, it changes the way you say the word.
Let's say you were speaking Spanish and you saw the word "café". The accent helps you pronounce it correctly. Without the accent, you might say "cafe" (which means cafeteria) instead of "café" (which means coffee).
The accent mark tells you which syllable in the word should be said louder and with more stress. In the case of "café", the accent is over the letter "e", which means you should stress that syllable when you say the word.
Many languages use accent marks to help you say words correctly. Even English has some words with accent marks, like "résumé" or "naïve". They might seem a little tricky at first, but once you get used to them, accent marks can make it easier to understand and be understood when you speak a foreign language.