What does it mean to use “hg update” to get a consistent check?

Question

I accidentally ran hg update featurebranch while my working directory had changes. When he asked me to resolve merge conflicts in the first file, I immediately pressed Ctrl-C to kill the command. Now when I try to make an error, I get an error:

 abort: last update was interrupted (use 'hg update' to get a consistent checkout) 

What does this mean and how can I recover from this situation?

Answer 1

hg update -r . will update without operation for the working branch without changing any files and fix the error message.

_{I'm not quite sure how / why it works, so if someone explains that I will accept their answer.}