Learn French: Ils ont vu des choses incroyables récemment.

vu is the irregular past participle of the verb voir (to see). To talk about the past in French using the passé composé, you need a helping verb plus this past participle. Here, Ils ont vu literally means "They have seen."

Why is there a des before choses when the English translation just says "incredible things"?

In French, you almost always need an article (little words like "the" or "a") before a noun. Because "things" is plural and we aren't talking about specific things, we use the plural word des (which roughly means "some"). So, des choses means "some things".

Why is it choses incroyables instead of incroyables choses?

In French, most adjectives come after the noun they describe, which is the opposite of English. Also, because choses is plural, the adjective gets an extra -s at the end to match it, becoming incroyables.

Do I pronounce the 's' at the end of Ils here?

Yes! Normally the -s at the end of Ils is silent. However, because the next word (ont) starts with a vowel, you link them together. The -s makes a "z" sound, so Ils ont is pronounced like "eel-zohn".