Learn Arabic (Modern Standard): نحن نشاهد أولئك الراقصين في المهرجان. - We are watching those dancers at the festival.

أولئك (those) is the plural demonstrative pronoun used for people who are far away. It is perfectly gender-neutral, so you use exactly the same word whether you are pointing at a group of male dancers, female dancers, or a mixed group.

Why does الراقصين have the definite article ال attached to it?

In Arabic, when you want to say "those dancers" as a single phrase, the noun after the demonstrative must be definite, which is why it gets ال. If you leave out ال, the phrase turns into a complete sentence meaning "Those are dancers."

Why is the word for dancers ending in -ين instead of -ون here?

Because it is the direct object of our action. The verb is نشاهد (we are watching), and the dancers are the ones being watched. For regular masculine plural nouns, the ending changes from -ون to -ين when they are the object of a verb.

Does نشاهد mean "we watch" or "we are watching"?

It can mean both! Modern Standard Arabic doesn't use a separate grammar structure for ongoing actions like English does with "are watching". The present tense verb نشاهد covers both "we watch" and "we are watching", and you rely on context to know which sounds best in English.