I'm trying to get my head round this. I'm practicing positioning shots. If I want to hit the cue ball on the side, top, bottom etc do I need to aim slightly off for example hitting an angle to accommodate my strike.
The general principle is that striking perfectly through the centre will send the ball straight. Any spin that it develops will be exactly that of the natural rolling of the ball across the felt when it eventually gains grip.
If the ball is struck off centre, the ball will have spin that is in the direction from the centre through the actual point of contact.
If the strike is directly below the centre, the ball has backspin, and if directly above, will have topspin. A strike directly to the left or right will create spin in that direction. A combination of above/below and left/right will have spin that is also a combination, though neither direction will be as rapid.
Regardless of where you want to place spin, the cue should remain parallel with the direction you want the ball to cue. A hard stroke will send the ball skimming with the spin provided, while a softer strike can potentially send the ball off to the opposite side rather than straight.
The best way to practise and learn how a given stroke will spin the cue ball is to practise sending it at right angles into the cushion, and observing the path it takes out, for different amounts of power and follow-through and offset from the centre.
You're asking about the topic 'cue ball deflection' or 'squirt'. Pool players talk about this a lot, snooker players not so much. Google those terms and you will find many explanations - Dr Dave Alciatore's site is an excellent resource.