A silencer and suppressor refer to the same type of device. A device that attaches to the barrel of a firearm to reduce its sound signature.
While the original name was in fact “silencer” (referred to as such by the inventor Hiram Maxim) the term “suppressor” has come into use in recent years (since 1985, US Patent 4530417) as it truly is a more correct descriptive term for the device. To say that it “silences a weapon” is quite an exaggeration if you are to take it literally. Suppression is a much better description.
Is it like the movies?
No. In Hollywood silencers are usually portrayed very unrealistically as a device that renders the weapon nearly undetectable by human ears. Thanks to a great study done by the Military Arms Channel in 2015 we have data available for several different suppressors that are currently on the market in .30 caliber. Their results show that the same rifle shooting un-suppressed (no suppressor or silencer attached) shot at an average of 170 dB. According to DecibelCar.com that is a little bit louder than the sound of a Boeing 727 at take off. When different models of suppressors were added the sound signature was reduced to an average of between 137-146 dB. Which, again according to DecibelCar.com, is right on the edge of hearing safe and not hearing safe (not using hearing protection). Anything but quite. Just a little less loud. The use of suppressors in the civilian market is largely to help save the users hearing.