What are the tales about faeries in the catalan region?
There are different beings in Catalan legends that could be equivalent to fairies.
I think the beings that are closer to faeries are the many kinds of "small peoples". The most famous ones are follets (a word that derives from "little crazy people"). Follets are usually tiny beings, similar to fairies but without wings and usually imagined as male. But they can also be human-sized sometimes. They are naughty and will torment you just to have fun, but they can also be very tidy and clean. Sometimes it's said that they fly because they're tiny enough to get carried by the wind, so they ride the wind breeze.
There are other kinds of small beings related to follets, for example minairons (so tiny that hundreds of them are stored in a needle tube, they ask for work and if you don't give them work or put them in the needle tube again they'll kill you), donyets (who braid horses' tails), or negrets (they turn into coins if a mortal touches them with a candle). I've talked about those three before on the blog, so click the links if you want to see those posts. There's also a more in-depth post about follets.
There are many more kinds of follet-like creatures, for example homenets / donetes de sa colzada ("cubit little men/women") in the Balearic Islands. They're people who are as tall as a cubit (30-40 cm). They have long white hair and beards, wear silk dresses and are very hard workers. They live underground and appear from caves and wells, or can appear when they're called. They always move in groups and can do work that is impossible for humans. They often appear in Balearic tales and are helpful to the main characters. After their work, you have to pay them fairly and then they go back to their underground.
A separate being that could be considered related to faeries are dones d'aigua ("water women"), also calles aloges, encantades (derivation of the word for "spell"), paitides, or dones de fum ("women of smoke") depending on the area. They are women who live in the ponds, stream pools, the fountains at the birth of a river, caves with underground streams, or any other places with water that are hidden in nature. They have very long lifespans and the appearance of beautiful women with long hair. Sometimes the long seaweed in the rivers and streams is said to be water womens' hair, so you have to be careful that your feet don’t get trapped in them because they can pull you down and drown you. It's said that they can be seen washing their clothes or combing their hair, most easily on full moon nights or on Midsummer night (the night of Sant Joan, according to Catalan legends that's the most magical night of the year and when you're most likely to run into magical beings), but you have to be careful and stay hidden. From time to time, one of them falls in love with a human and they get married and move in together, sometimes even have children together. However, the dona d'aigua always ask the man to keep a secret that she's a water woman, but eventually the man tells someone and the water woman runs away taking the child.
Oh! And there's also our equivalent of the Tooth Fairy. In the Catalan Countries, it's the angelet de les dents ("Little Tooth Angel") or simply the angelets ("Little Angels"), or the follet de les dents ("Tooth Follet"). Sadly though, I think in many families these traditions are very quickly being lost over just one generation. While most people in my parents generation had their milk teeth taken by the Little Angels, in my generation and the younger ones many have replaced it with the Spanish version, which is ratoncito Pérez ("mouse Pérez" in Spanish). I say "sadly" because this is part of a general trend of losing some Catalan traditions that become associated with old people, while the Spanish or North American ones are seen as cool and trendy because of the media influence and the underlying ideas resulting of the historical discrimination of Catalan culture.
As for fairies in the English understanding of the term, I think they became popular later when upper class people read the Germanic tales. There is one, though, and she's relevant. I'm talking about Flordeneu (the name means the edelweiss flower), a character in Jacint Verdaguer's 1886 epic poem Canigó. This is one of the most important books in Catalan literature, which talks about the birth of Catalonia in the Pyrenees during the Carolingian period, but it's told through characters from legends.
In the book, the main character is a knight called Gentil who hears about the fairies that live in the Canigó mountain. He decides to go up the mountain because he believes he will be able to find a talisman that will allow him to be with the girl he's in love with, a shepherd called Griselda who Gentil's father banned him from seeing.
Gentil is received by Flordeneu, the queen of the fairies of the Pyrenees, but she is disguised as Griselda and fools Gentil. Gentil abandons his search for the talisman and instead follows Flordeneu to the underground palace of the fairies, made with crystal columns and marble arches, with freshwater streams and ponds running through it. Then they fly over the Pyrenees on a chariot pulled by deer and come back to the Canigó to get married. Flash forward to the end of the book, a cross is planted at the top of the mountain and the fairies are expelled, because then they are understood as evil beings who are enemies of Christianity.
I hope this was interesting to you and answers your question. You can find more about Catalan mythological beings and legends in this blog's tag #llegendes.