Hub and spoke in regards to the CCNA, is probably describing a common Frame Relay/WAN network setup.
Say you had 6 seperate sites you had to connect. It would take 15 circuits to have full connectivity between them as a full mesh, and it gets worse with the more sites you have.
Hub and Spoke is taking 1 site, and connecting all sites to it, to trasit that site to get to each other. This way, 6 sites can have fully connectivity with only 5 circuits.
So say you have sites A,B,C,D,E and F, with site A as the hub and B,C,D,E,F as the spoke would connect to site A, and use site A to get to each other.
You can say partial mash network as a hub and spoke network.