Crankset question

[Catrin]

Wasn't sure where to put this... Next Friday my fitter and I are meeting to start the conversation about how to build my bike up. He is going to put together an initial parts list after we discussed it - the purpose of the first list is to both start the discussion and to give me a somewhat realistic idea what the cost will ballpark.

I think my biggest, and most difficult decision, will be whether to go with a triple or a compact double with a mountain cassette. I want the deepest range of gears I can have, and there are several ways we can approach this. I don't want to open that debate in this thread, there are plenty of other threads that I can read about that - both on this forum and on others.

What I am trying to understand right now is more basic. As an example, the crankset on my LHT is a 48-36-26t. What do those numbers actually mean? I know about Sheldon Brown's gear calculator and I will be putting in a lot of time on this - and I've a basic enough understanding of the rear cassette. It would be helpful to me to better understand what those numbers mean on the crankset description.

Are the numbers, basically, the travel distance for the chain between each of the three large rings? If this is correct, then how would smaller, or larger numbers on the crankset affect my overall gear choice? I've looked for links, but can't seem to find something basic enough