T3 and E3 standards offer higher bandwidth than their T1 and E1 predecessors. T3 stands for T-Carrier Level 3 and is a type of connection usually based on coaxial cable and a BNC connector. This differs from T1, which is usually offered over twisted-pair media.
T3 connections are often referred to as DS3 connections, which is related to the data carried on the T3 line. T3 offers additional throughput because it uses the equivalent of 28 T1 circuits, meaning 672 T1 channels. This offers a total line rate of 44.736Mbps.
E3 connections are similar to those of T3, with the exception of being equivalent to 16 E1 circuits, meaning 512 E1 channels and a total line rate of 33.368Mbps.
T3/E3 connections are usually used in large data centres because they offer the ability to increase the total amount of throughput when needed.