Can anyone explain me the difference between the first two? I can see when i go to docs that it says CURRENT next to Hoxton.
I guess the third is going to be released this year so not many people can tell me what is going to be new and different.
Greenwich is not supported anymore. Hoxton is a supported GA release train (that's why its releases are marked as current = the most recent GA release). Service releases are being done for that release train. 2020.0.0 (previously called Ilford) is the release train that is currently under development - the first milestone (M1) has been released and M2 will be coming next.