Transmission is a BitTorrent client. It is used for peer to peer filesharing over the internet. BitTorrent is a fast way of transferring files, because everyone who downloads must also upload to others, thus creating much more bandwidth than a single server offering the file may have been able to provide.

You'll need to download a torrent file (extension .torrent). These are commonly found at 'tracker' websites. Torrent files contain information about the actual file you want to download (eg a movie). Once you have the torrent file, open it in Transmission. You can also set Transmission to open torrent files automatically via Preferences >> Transfers >> General.

It is good etiquette to 'seed' the file for a while (ie leave it uploading) once your download is complete. You can set a default ratio to automatically seed to, and then pause. This can be adjusted in Preferences >> Transfers >> Management, or in real time using the Action menu.

Follow the instructions here.

Yes, by using 'Speed Limit Mode'. Simply go to Preferences >> Bandwidth, and then set both the speed you would like Transmission to be limited to, as well as the period of time you would like the limits applied.

When Speed Limit Mode is enabled, the turtle will be illuminated in blue.

Yes, via Preferences >> Transfers >> Management.

The queue system is very simple: You start and pause transfers as usual, but if you're over the queue limit starting a transfer will instead make it "Waiting to Start". You can force a transfer to start without going in the queue by holding down option and clicking resume or using the Transfers menu item "Resume Selected Without Wait". The queue system only applies to non-seeding transfers.