Hows does a thermos keep things hot and cold in terms of conduction, convection and radiation

Conduction:
air, and other bad conductors are kept between the substance inside and outer environment(that is the lining cavity)

Convection:
air in touch with the substance is sealed(cant really move).

Radiation:
the inner surface are silvered to reduce radiation

I am not 100% certain how a thermos works but when they first came onto the market my fishing partner bought one. We were fishing and at lunch time we got our food and drink out and I asked my friend what the strange object was, he said it was called a thermos flask. I asked him what it was used for and he said it was very good at keeping hot things hot and cold things cold. I said it was a brilliant invention and ideal for fishing, what did he have in it, my friend replied that he had two cups of tea and a choc ice in it.

Energy may be lost to surrounding by namely
1.conduction'
2.convection
3.radiation

A thermos avoids all the possible ways the energy may be lost..and hence keeps hot and cold as such.