When we use active voice, there is a subject that does the verb in the sentence.
The people of Quinamayó celebrate Christmas. (Subject= the people and they are the ones who celebrate)
However, if exactly who celebrate is not important, we might use PASSIVE voice instead.
Christmas is celebrated in Quinamayó. (Subject = Christmas. Who celebrates is understood or not important.)
In Spanish there are two ways to create passive voice:
Se celebra la Navidad en Quinamayó.
Se celebran los festivales afrocolombianos.
The verb conjugates based on what is being celebrated here: singular for la Navidad and plural for los festivales.
Note these do not say literally who celebrate (“the people”) because it’s either understood or it’s not important in the sentence.
If I want to include who, I can add “by…”
Se celebra la Navidad en Quinamayó por la gente afrocolombiana.
La Navidad es celebrada en Quinamayó.
Los festivales afrocolombianos son celebrados por la gente.
This form is more like a literal translation of English: Christmas is celebrated... The festivals are celebrated...
This participle forms just like with the present perfect tense: celebrar = celebr+ado. However, the participle here acts as an adjective and must match what it describes.