"Delta" meaning

Hi everyone!
I'd like to know what is the meaning of the "delta" number, anyone knows that?
it is known next to the "Elo" number after ending one match
thank you

@Akelakaa It is the amount of points you gained or lost But I have no idea how it is determined...

@Akelakaa
The basics of the elo rating system is described here:
https://en.m.wikipedia.org/wiki/Elo_rating_system
The catan specific part is explained here in the faq section.

thanks!!