Generally correct, except "squibs" have two different meanings related to movie production vs. firearms.
First, a movie production squib is a loaded "bag" containing fake blood and a small explosive charge (or air compressed) placed upon/within a costume, glass or metal that is triggered remotely to give the appearance of a bullet hit.
Second, for a firearm, a squib round is a bullet that has been fired from it's casing (shell), but gets lodged in the barrel due to a reduced powder load or related ammunition issue. Therefore, if another round is fired after after the squib load and hits the original round stuck in the barrel, the potential for a catastrophic malfunction exists (ie: the barrel bulges or explodes).
Most movie guns are real firearms that have been modified to accept only blank rounds. Usually at the muzzle with adapters that modify the sound, flash and recoil (depending on the scene). Many are also modified at the chamber to prevent live (real) bullets from being loaded.
However, a blank round CAN cause severe injury or death at close range.
Just my two cents.