I want to contribute to the xubuntu community, ideally triaging bugs but I fail to really understand this page. Does that make me a useless (x)ubuntu user in terms of helping developers? :(
No it certainly does not mean that you can not be of some help. Don't lose hope... You just need some time to get to understand bug reporting... :-)
Triage is simply were a bug is "placed" upon being found. Once it is there, then someone will decide what to do with it, and mark it appropriately. Once it has been marked, it is considered to be triaged
For example, if you think you have found a bug, strange as it may sound, it may not be a straight forward bug. Not all bugs, or issues are actual bugs. It could be a feature (or lack thereof) that you assumed would be there, but isn't yet in the design. In that case, the bug is actually a feature request.
If a code change has made something stop working then that is a regression as the code has regressed.
Apport bugs are reported automatically by an app when something is detected to have gone wrong. Similar to a Mac crashing and then asking to send a Crash report to Apple.
Confirmed bugs are issues that are nearly ready to be triaged but something is missing: complete reproduction steps (how to make the bug happen so that the developer can investigate it), or it similar to a bug already being worked on.
Duplicate bugs are bugs that have already been reported. The information from the new report may be more informative that the existing bug report, in which case the original bug report should be updated with the new info, and the latter bug report marked as duplicate.
If a bug does not fall into a convenient category then it may sit around in triage for some time, until someone decides what to do with it. In that case it is Untriaged.
These include developer bugs (which are more like personal notes for the developer themselves, to remind them the state of the bug as they work on it), needs-packaging (which means that some code needs to be rolled up in a package for ease of installation), security bugs (self-explanatory) and translation bugs (for localised applications - for example to app may have an English interface, but lack one in German).
I hope that this helps.