So much bicycle acronyms and initialisms makes for a challenging read for the uninitiated (like myself)! I've researched the terminology and happily share in hopes you too will find it useful:

1. "lower BB" references a lower bottom-bracket, the part that holds the axle to which the cranks attach.

2. "CX", or cyclo-X is short for cyclocross, which is a style of bicycle race which takes place over varied terrain conditions such as pavement, wooded trails, grass, steep hills and obstacles requiring the rider to quickly dismount, carry the bike while navigating the obstruction and remount.

https://en.wikipedia.org/wiki/Cyclo-cross

https://en.wikipedia.org/wiki/Cyclo-cross_bicycle

The cyclocross bikes appear similar to road racing cycles, the major differences between them being frame geometry, and wider clearances for cx bikes to fit larger tires and generally still function after accumulating large amounts of mud and other debris.

edit: Thank you @jerrycrunch! I've incorporated your bb info.