As with the guitar, there's multiple ways to play a few notes on this instrument. The most common ones, when we get to B-flat in the middle and the second octave of the horn, we've got A, and we've got a side B-flat key here to make the A a B-flat. I've got the side B-flat on and I'm fingering A here. Another way to make the same note is to use this key, which is the little key underneath the B key. We're just holding that down like that. Same note, different fingering. Another way to do the same thing again is to just play the B as normal here, but on the right hand I'm going to hold down a F, which you see actually brings down this key here. Three ways to play the same note. And of course this is the same with the octave key on. There's actually a fourth way if we play the low B-flat and put the octave key on.
You've got to figure out where you're coming from and where you're going in relation to the musical passage you're performing, and figuring out the best fingering option to use. For example if I'm playing this, the best thing to use there is the side B-flat because our next note is a C. It'd be a little awkward if I used this, for example. See, that's not as clean as... You can hear the little discrepancy in there.
Another common note that has multiple ways to produce it is C. The first one you would learn is middle C, like this. There's no octave key on this in the middle of the horn. It's just the middle finger. Same way to produce that note is if we play B and we use this middle side key here. Same note, different fingering. I would use the side key if I'm playing something like... Nice and smooth, right? If I were to use the forked or in the middle C here, that's going to be a little funky...as opposed to... Whereas the forked would be great for something like... The side would be weird there...
It's important to know all the ways to play all the notes on the saxophone because you're going to need those options and they're really going to help you at some point.