Learn Spanish (Latin America): Aquí falta algo.

Algo means "something." It is an indefinite word used when you aren't referring to a specific, named object. In this sentence, it acts as the subject, so the literal translation is "Here, something is lacking."

Why do we use falta instead of translating "is missing" word-for-word?

English uses the verb "to be" plus the word "missing." Spanish just uses the verb faltar, which means "to be missing" or "to lack." So the single word falta does the job of both English words!

Why is algo at the end of the sentence?

Even though algo (something) is the subject here, Spanish is very flexible with word order. With verbs like faltar (to be missing) and gustar (to be pleasing), it is extremely common to put the subject at the end. You could say "Aquí algo falta," but "Aquí falta algo" sounds much more natural to native speakers.

How would I change this sentence to say "Nothing is missing here"?

You would swap algo (something) for its exact opposite, nada (nothing). In Spanish, if the negative word comes after the verb, you also need to put no before the verb to make a double negative. So you would say "Aquí no falta nada".