Will write a proper description without a terrible amount of typos at some point.
Watching = Series I'm currently watching; mostly very long series or series that are currently airing. Will move to Stalled if I stop watching completely for around 3-4 months and/or forget what's going on and/or if I don't feel like finishing the series for whatever reason.
Stalled = Series I'm planning on finishing some day. I make no promises to myself when to finish them. In 99% of the cases the series stay stalled for years and I end up watching them from the beginning because I can't remember the past events. Also in about 90% of the cases I won't actually continue these series and I just start watching new ones instead. Too much anime in the world...
Dropped = Series that I found so terrible I don't plan on finishing. I might come back to these after I finish all my stalled series, but somehow that seems very unlikely...
Watched/Won't watch should be self explanatory. I try not to put anything in the won't watch category though.