Definition - What does Strain Relief mean?
A strain relief is a standard fixture for electrical cables that functions as a feature for relieving the stress from the cable connections themselves to prevent them from breaking. It is located in the base of the connector where the connector meets the cable and usually comes pre-molded as part of the connector itself. It is the part of the connector that looks like a sleeve over the cable and is often segmented to allow some limited bending without problems.
Techopedia explains Strain Relief
The strain relief, as the name suggests, relieves a cable of stresses and tensions that could break the conductor inside or the connection between the plug or connector and the cable. It is an essential feature for the mechanical and electrical integrity and overall performance of all types of electrical cables. The usual design found in consumer-grade cables is often the overmolded strain relief, which is already part of the connector itself, and looks like a segmented sleeve over the portion of the cable attached to the connector.
On other cables, especially those that are manufactured separate from their connectors, strain relief often comes in the form of a separate device that is installed over the connector and the cable joint. In the case of network cables, the strain relief is called the "boot," which is fitted over the connector after attaching the cable and the RJ-45 connector. In other connectors, the strain relief can be in the form of metallic connectors and grips, some of them made of metal that are crimped over the cable to provide tensile strength.