twisted pair

This is from the days of low frequency transmission such as audio. The twisting reduces capacitive and inductive pickup. This type of line was cheaper and more flexible that coaxial types. An in between type is shielded twisted pair.

they are the simplest and chipest time of transmition line. the are used widely in 1960s and now they are rarely used.
regards

Rarely used? Like telephone and ethernet?

Look inside any modern computer. Many high MHz and GHz twisted pair links.

Differential noise immunity. Easy and cheap to manufacture.

Man, I wish I had 0.01 cent for every foot of CAT5 twisted pair manufactured each year!