Short answers, pulled from the story.
Live action refers to cinematography or videography that uses real photography instead of animation. According to the Cambridge English Dictionary, it involves real people or animals, not models, drawn images, or computer-generated imagery.
The term is applied to adaptations from animated cartoons, video games, or comic books to signal that human actors and real photography are being used instead of animation. Without the label, audiences might not know whether a studio has cast performers or produced another animated feature.
No. Disney's 2019 remake of The Lion King was rendered entirely by computer with no real animals and no human performers on screen. Several media reports described it as live action, but critics noted this was an error by the Cambridge English Dictionary definition, which excludes images produced by computer.
Within a mixed production like Who Framed Roger Rabbit, "live action" refers specifically to the human performers, such as Bob Hoskins, as opposed to drawn animated characters like Roger and Jessica Rabbit. The term distinguishes which figures were photographed from which were animated.
Live action involves real actors, sets, and props, making productions feel personal and close to reality, but costs are constrained by budget. Animation can convey abstract ideas that would be impossible to photograph but generally takes much longer to produce.
Michael Jordan appeared as the live-action lead in Space Jam alongside animated characters. Julie Andrews performed as the live-action title character in Mary Poppins alongside animated sequences.