Simply put, silencer and suppressor are synonymous. Depending on the conversation and the person involved, “silencer”, “suppressor”, “sound suppressor”, and “sound moderator” are all interchangeable terms for a a device which reduces the amount of noise and visible muzzle flash generated by firing a gun.
Suppressors are typically constructed of a metal cylinder with internal mechanisms to reduce the sound of firing by slowing propellant gas which occurs during shooting a firearm.