The most important stroke in the game is the break off. Unlike in pool, you don't smack it as hard as you can in the hope of sinking a ball. There are no limitations on cushions you must hit etc. So, players will break off in such a way as to prevent their opponents not having a chance to pot the ball, and hopefully, not leave an easy return safety shot. Safety shots are not frowned upon in snooker! The tactics are an important part of the game.
Rather than explain the intricacies of the break off, I'll let two former World Champions, Ken Doherty and Shaun Murphy explain for you. Murphy's actual example of a break off is terrible, he hit the break terribly, a red would have come up the table had he hit it hard enough, and it was short even of the baulk line, let alone the baulk cushion (where he was aiming). Baulk is the line with the yellow, green and brown on it. Nevertheless, they have a good discussion about the break off, which is well worth a listen.
A better example of the breakoff comes here. It shows the advantage of getting the cueball tight on the cushion, as O'Sullivan could only play a negative safety into the back of the pack of reds off two cushions. But even then, Hendry potted a red. The whole chance was created by the break off shot. The commentary from Willie Thorne and John Virgo is illuminating. You need only watch the first 1 minute and 50 seconds or so. Hendry went on to lose that frame, but that was an error later on. You can see how a good break off led directly to giving him an ideal opportunity to win the frame.
Here you can see how when you bring a cueball back to the baulk cushion, even though he brought a red down the table, Hendry was left with no option but to go for the pot. Hendry had to try a pot, which he missed. O'Sullivan went on to win the frame.
Conversely, you can see how O'Sullivan bundled this break off against Allister Carter. Hitting the blue meant that Carter had the first chance of the day. He went on to lose the frame, but again you can see how a bad break can give your opponent a big chance. The first minute and a half is the introduction at the start of the session, after that the instructive bit begins.
I hope you enjoyed the instruction on how to break off! If you want to see more videos, look on YouTube, and search for World Snooker Championship 2008, you'll find loads of O'Sullivan videos, I recommend his match v Stephen Hendry. Feel free to ask questions...