There are many misconceptions spread by Hollywood movies and video games about gun suppressors. Many of these misconceptions are quite prevalent.Firstly, the technical term is indeed "suppressor", not "silencer", although this is mostly a nitpick. There's nothing inherently wrong in using the latter term, but if you want to use the technically correct term, it's "suppressor".
This is a bit more common knowledge, but not to all: Suppressed guns do not make that "pew pew" sound that's so common in movies and many video games (a sound that would imply that the shooting of the gun makes absolutely no sound, and the sound is solely coming from the bullet traversing through air at a very high speed.)
Suppressed guns do make an explosive sound, just a greatly diminished one. Rather than sounding like a loud explosion, it sounds more like a small firecracker, or like slamming a ruler against a table. The volume of the sound is only a small fraction of the non-suppressed sound, but it's still clearly the sound of a shot. Even so, it can still be highly beneficial if the intent is to cover the sound of gunfire, as it might not sound like a typical gunshot even from the next room. And it may not be heard almost at all farther away (from a distance where a regular gunshot could be very easily heard and recognized.) If you slam a ruler onto a table, your neighbors probably won't hear it. However, you certainly can't fire a suppressed gun behind a person without him hearing it.
One much less known and understood fact is that suppressors do not slow down the bullet. This misconception is especially prevalent in many video games, where using a suppressor will make the gun cause less damage, or even reduce its firing distance.
This is not so. Suppressors do not touch the bullet (that would be quite counter-productive, and completely unnecessary.) Thus they do not slow it down in any way. In fact, the opposite is actually true. Not by a big margin, but measurably so: A suppressor may increase the exit speed of a bullet by up to about 5%. (This is because the suppressor effectively increases the barrel length, and a longer barrel, up to a certain point, increases the exiting speed of the bullet.)
Note that in some cases, in real life, a different type of ammunition is used, in conjunction with suppressors, to reduce noise even further. This ammunition has less gunpowder and thus makes less noise, but causes the bullet to be fired at a much lesser velocity (even at subsonic speed, thus avoiding the "sonic boom" that a normal bullet could make.) The misconception that it's the suppressor itself that causes the bullet to slow down might have originated from this.
On a somewhat of a side note, in real life, at many places, when police special forces storm eg. a drug lab, they will often use suppressors in their guns. Many people don't know the real reason (and have all kinds of misconceptions about) why that's so. It's not about being covert (obviously a group of special forces storming a compound is anything but covert) or anything like that. The real reason is to lessen the risk of flames from gunfire igniting flammable gas that might be present in the lab. (Suppressors are great at dampening flames from gunfire.)
