Within these two basic categories are subcategorizes. Download data from G.dmt ADSL at the rate of 8 megabits per second and upload data at 1.5 megabits per second. G.dmt ADSL is the fastest, but needs to be within 10,000-12,000 feet of the phone company's central office. For up to 18,000 feet from the central office requires a device called a splitter on the phone line requiring an installation visit to your home. ADSL is the standard.
Main difference is speed and self installation.
Download speeds up to 1.5 megabits per second and a maximum upload data rate is 384 kilobits per second. The major disadvantage is that it is unacceptable for voice and entertainment applications. The main difference is the capability of adjusting bandwidth to the quality of the phone line during the data transmission verses just once at the beginning. Symmetric DSL is for business, provides the same rate both ways. Best suited for web servers, corporate networks and those who send large amounts of data.