I hve been reading the manual and I’m finding it hard to understand what is meant by ‘busses’ and groups. To my understanding, groups means you group together instruments, for example all lead guitars plus double tracked parts into one group and this allows you to mix/control volume for the group of instruments rather than each individual instrument, have I understood this correctly? Now when it comes to ‘bussing’, I have no idea or understand, so appreciate if someone can explain it in simple terms. Thanking.

In your context you can think of a buss as a connection that can have multiple signals routed to it. (or from it)

So in your example, a group channels input is a buss or an FX input is a buss and you use sends from each channel to route that channels signal to the send buss, or the master output, commonly called a master buss or summing buss as all the channels are routed to it.

The confusion may lie in the terms group and buss, a group is a summing buss so is the fx input and so is the master fader etc

Buss actually refers to a physical rail or conductor with multiple connections feeding to or away from the buss, but in digital terms it’s still handy to think of it this way.

Think of a bussbar like a main road with side roads, the main road takes you to your destination and all the little side roads allow everyone to merge onto the main road and get to the same destination (or different destinations but all along the same main road)

It comes from the term busbar