Un servidor is a cutesy way of refering to yourself in the third person. It is commonly uttered by radio announcers. The idea is something along the lines of your humble servant or yours truly. I mention it because it is confusing the first time you hear it. Un servidor habló con tal fulano …, I (yours truly) talked with so-and-so ….
I once heard a customer approach a counter and ask for a colleague by name. The person responded with servidor, meaning Speaking. That’s me. I’m the person you’re looking for. On this phone this would be: él/ella habla.
Some people, upon meeting you and giving their name, will add para servirle. Literally this means at your service, a sus órdenes, although in reality it is merely a polite formality. A version with tú is also heard: para servirte.
A sexoservidor(a) is a prostitute.
A barber may say servido, you’ve been served, to indicate that the haircut is over. A tamalero once said this to me upon handing me a bag of the tamales that I had just ordered to go. To a group of people as they get out a taxi, the driver might say servidos, in plural.