I'd highly recommend the Logic 101 course. Stick with it, even if you're not interested in synths and the like as many of the techniques taught in this course will enable you to not only understand Logic Pro much better, but also feel comfortable using the software to record, arrange and mix any style of music.
I'd highly recommend the Demo to Master course as you can use the generic tips taught there in any DAW.
In Logic an input corresponds to the input on your audio interface. So when recording audio into Logic you'd need to set up the audio channel strip with the correct audio input which you have your guitar or mic plugged into.
A bus is commonly a channel strip type. In Logic 9's case, a bus can be thought of as a virtual connection. So for example, let's say you record 3 takes of your voice on separate tracks so you can process each for a chorus effect... rather than processing each vocal track with its own instance of a reverb plug-in... you can route all 3 tracks's outputs via a Bus into an Auxiliary channel strip and place one reverb plug-in on the Aux channel.
The Bus, in Logic, is the internal connection where the audio signal travels through... again, you'll find out all about busses and Aux channels in the Logic 101 where you'll be able to see and hear how this works :)