On earth, blankets serve to primarily buffer temperature changes / heat transfer that would occur via convection (e.g. a blanket traps air near you so that after your body warms it, it doesn't just get blown away and replaced with cooler air), and conduction (e.g. if you're lying on ice, a blanket between you and the ice with poor thermal conductivity will slow the rate of conductive heat transfer).
In the case of a free-floating spacecraft in the vacuum of space, convection and conduction don't exist, and temperature / heat transfer are dominated by incoming radiation (from the sun) and outgoing radiation (radiative black-body cooling from the spacecraft, if I'm using that term correctly). (To be clear, conduction does exist in space between objects that are in physical contact, but I'm talking about heat transfer through the surface of free-floating objects for the purpose of this question).
How are space blankets designed to buffer radiation? In the simplest form, I imagine a space blanket would be a thin material that's separated from the spacecraft skin by a thin layer of vacuum, i.e. it would only exchange heat with the outside environment and with the spacecraft via radiation, and so the goal would be to minimize the radiation accepted from the spacecraft and emitted towards the spacecraft. Do space blanket materials simply have a poor capacity to absorb and emit radiative heat, i.e. they're super reflective? Or is there more that factors into their design?