The following article explains how the RJ45 connector works. There are many different types that work with different networks. There are even distinctions between the cables that make them more or less flexible.
The stranded cables have thin filiments that create a wire that is easier to bend than the solid cables, which consist of a single copper wire. It is important to match stranded or solid cables to ensure a good connection. A solid connector only matches with one cable whereas stranded cables connect to multiple wires that are round together. They are not interchangable.
You can determine which type of cable you have by examining the teeth in the connector. Solid connectors tend to have longer teeth than stranded ones would.
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Solid and Stranded RJ45 plugs