Mobile Broadband?

Scorpion asked:

I am pricing laptop computers, and I noticed that many offer options for mobile broadband. What I don’t understand is why I would need it! If my (potential) laptop has a wireless card, isn’t that all I would need to access the internet? What is the advantage of mobile broadband?

By the way, I know that a wireless card can only access the internet at a hotspot, and I know that mobile broadband requires a subscription service.