"Sync FAQ"
Syncing is what you do when you record a computer signal that either tells you the time, or the beat, and then use that signal to keep equipment in synchronizity to each other. Your 414 has a sync connection, to where you connect the equipment that generates and interprets that type of signal.
There are basically two types of sync: Beat sync, and time sync. Beat sync is basically a metronome recording, i.e each beat (or rather, each 96th note) a signal is recorded and then the equipment uses this signal to keep the beat.
Beat sync is easy to do, but usually has the disadvantage that you always have to play the song from the beginning.
I don't know of any open standards for this except "Roland sync", used by old Roland equipment. Otherwise each piece of equipment uses it's own standard.
Time sync doesn't record the beat, but instead records the time. The dominating standard for this is SMPTE, which is made for movies, and therefore continously records the time (hour:minute:second) and the frame number within that second. The good thing about this is that you can easily sync things that isn't based on beats, like two tape recorders, and you don't have to start from the beginning, since you always know exactly where you are. The drawback is that your sequencer has to understand SMPTE or MTC, which is basically SMPTE converted to MIDI. Cheap equipment usually don't do this.
There is also "Smart sync" which is some kind of mix of the two. I haven't used it and know little about it.