What is a adsl broadband?

To understand first you need to know that there are two forms, Broadband and Baseband

Broadband is a form of transmission in which signals are modulated as radiofrequency analog pulses with different frequency ranges. Unlike baseband, broadband technology does not involve binary encoding. The use of multiple frequencies enables a broadband system to operate over several channels and, therefore, carry much more data than a baseband system.

ADSL is Asymmetrical Direct Service Line- in which you get more information downstream than upstream throughput. in other words you have more data that you can receive than you can send.

for example you can receive data at 5mbps but can only send data at 1mbps.