The are twisted pairs inside metalised plastic or a foil and plastic screen.

The blue/silver colour is the screening wrap, inside are two cores twisted, and usually a bare wire that hits the foil where it touches and acts as a screen connection (the so called 'drain wire').

Ideal for low current analogue and digital links - which for genset start-up interlocks at 12 or 24volts are an OK sort of thing.

Folk who are not sure how to terminate that foil and drain wire and just cut a tail end and leave it flapping about to catch the back of your hand or worse  poke into something energized are a bit of a liability.  Ideally the drain wires should be earthed at one or both ends, and if the other end is not earthed then a bit of heatshrink over the end where the twisted pair emerges from the foil, and over any bare foil, works wonders for the health and safety.

These sort of  cables  are quite flexible and a bit beefier in terms of current handling than Ethernet type cables, but with non-guaranteed high speed performance but electrically similar , unofficially OK for CAN bus, RS 488 and similar industrial comms links.. What is not really right is to use offcuts of the wires  within for mains rated hook-up as they are not normally mains rated, and it is not clear if that has happened.

Mike.