Limiting flash and report and drastically reducing the sound levels of firing rounds, silencers (or, more accurately, "suppressors") are a useful tool. Friendly to your ears and the ears of those around you, using a silencer is the polite way to shoot.
Silencers function by allowing the hot gases trying to escape the barrel of a firearm to dissipate more than they normally can prior to exiting the chamber. They do this by providing extra space for the gasses to expand - hence the baffles on most silencers. This deadens the amount of noise and report of the firearm, but does convert this energy into heat - many silencers can heat up quickly under sustained fire, making the heat-resistant silencer cover a very popular silencer accessory.
We've sorted our selection of silencers by firearm type - but the sky is often the limit with how you can mix and match. For starters, make sure that the bore of the silencer you're looking at is large enough to support the calibers you're thinking of shooting through it. From there, ensure that the pressure level of the cartridge is supported by the can. For example, a SilencerCo 9mm Osprey bore is large enough to support a .30 caliber round - but is not rated to rifle calibers, so while a subsonic 300 Blackout round might be ok, firing a .308 Winchester round through that can will likely destroy the silencer.