Short answers, pulled from the story.
A film frame is one still image within a sequence that makes up a moving picture. When frames are displayed in rapid succession, a phenomenon called persistence of vision blends them together so that the eye perceives continuous motion rather than individual photographs.
Standard film projection runs at 24 frames per second. Silent films and 8mm amateur movies used slower rates of 16 or 18 frames per second, while special venue systems such as IMAX, Showscan, and Iwerks 70 have used 30, 48, or even 60 frames per second.
The 29.97 frames-per-second rate traces back to the design of the Chromilog NTSC television system. That fractional difference from 30 creates synchronization issues unique to the NTSC world, leading engineers to develop workarounds such as drop-frame timecode.
Frame size varies widely by format. An 8mm amateur frame measures approximately 4.8 by 3.5 millimeters, while an IMAX frame reaches 69.6 by 48.5 millimeters. Standard 35mm motion picture frames are smaller than their still-camera counterparts because the film moves vertically rather than horizontally.
A still frame is a single static image extracted from film or video footage. Law enforcement agencies regularly publish still frames from surveillance videos to identify suspects and locate additional witnesses. Still frames from the film of the Kennedy assassination have been examined repeatedly by investigators seeking different interpretations of the sequence.
Animation has a tradition of characters interacting with the physical boundary of the film frame itself. Common gag types include split frames showing two frames at once, film break gags where the image disappears as if the reel has snapped, gate hair jokes where a character removes an apparent hair from the frame, and animated cue marks and editorial symbols. Inglourious Basterds used oversized cue marks for the reel changes of its Nation's Pride pseudo-documentary as a deliberate meta-cinematic effect.