For those who are not too familiar with these things, these are known to be routers. DSL stands for Digital Subscriber Link while ADSL stands for Asymmetrical Digital Subscriber Line. DSL would need to create an internet connection between a modem and a phone line. ADSL refers to the sending and receiving of data.
Whenever people send data to others, this would be known as upstream. Whenever people download data, this would be known as downstream. Take note that ADSL will usually have a faster download stream as compared to uploading. DSL and ADSL are almost the same but they are two different types of items that people may use now.