From Wikipedia:
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In communication networks, throughput is the amount of digital data per time unit that is delivered to a certain terminal in a network, from a network node, or from one node to another, for example via a communication link. The throughput is usually measured in bit per second (bit/s or bps).
The system throughput or aggregate throughput is the sum of the data rates that are delivered to all terminals in a network.
Often maximum throughput is implied by the term throughput. The maximum throughput of a node or communication link is synonym to its capacity.
The maximum throughput is defined as the asymptotic throughput when the load (the amount of incoming data) is very large. In packet switched systems where the load and the throughput are equal (where there are no packet drops), the maximum throughput may be defined as the load in bit/s when the delivery time (the latency) asymptotically reaches infinity.
The channel utilization in percentage is the achieved throughput related to the physical data rate in bit/s of a digital communication channel (also known as the network access connection speed, the digital bandwidth or the channel capacity).
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So channel utilization is expressed in percentage. Eg: if the throughput is 70 Mbit/s in a 100 Mbit/s(which is the physical data rate) Ethernet connection, the channel utilization is 70%.
In more general terms, in computer technology, throughput is the amount of work that a computer can do in a given time period. Eg: throughput theoretically tells you how much useful work the MIPS are producing.
Sumit