I notes there is a send track but whats the purpose of it and how is it useful? I notice you can send a note track to send only for effects but I can just add the dsp effects on the regular note track. How is this helpful for some one who wants to make drum n bass.
Is the Master track serve any real good purpose, I heard you need a pro to master a track. I want to at least try as professional as I can but I am not spending money to get a song mastered b/c this is a hobby.
one small example is, you can route all drumtracks to a sendtrack. then you are able to control the volume of all elements with one slider. or you can use a compressor on the sendtrack to compress all the drumsounds together and so on. it`s a must have for drum&bass but also for every kind of music 
Send tracks are also a neat way of grouping tracks together as one track for mixing purposes. Suppose you have many tracks where one track is the kickdrum, the other is the snare drum, the third the hihats, etc. If you send all these tracks to a send-track, you will be able to simply rename that send-track to e.g. “Drums” and then place an effect chain on that track which would apply to all the routed tracks (the kickdrum, snare, hihats etc) as if they were all on one single channel/track. If you would lower the volume in the mixer for that send-track, everything on that send-track would be get their volume lowered – i.e. treated as if it were a single channel/audio source.
The Master track is just a conventional way of saying “this is the sum track, the Super-Send Track”. If you put any effect(s) on the Master track, it will affect all other tracks (including the dedicated send tracks).
EDIT: Kasmo was faster… 
The main reason I use them is to temporarily use fx on tracks. Like, say, having delay or reverb on a single note.
If you leave the dsp on the track in question, when you turn off the effect it turns off the tail of the reverb.
Another common example is using a reverb effect on a send bus. You can then just mix various different instruments into the sends reverb [keep source] and save quite some CPU cycles, especially with convolution. The reverb should output only a wet signal, not dry. At least in a common song, rules can be broken. 
send tracks are an essential need for creating complex filter routings …See the thread vocoder , formant filtering
could you post up a link? i think iv seen the thread but want to make sure
Is send bus the same name for send track?
Thanks for your answers guys.
Practically, yes.
seen it, nice one btw