Short answers, pulled from the story.
A game demo on a 5-inch floppy disk in 1993 cost less than a cup of coffee. This low price allowed fledgling companies like Apogee Software, Epic MegaGames, and id Software to bypass traditional publishing barriers during the golden age of shareware.
Gaming magazines became the primary vehicle for distributing demos in the 1980s and 1990s, often including them on cover disks or tapes in the United Kingdom and mainland Europe. As broadband Internet became widespread, the practice shifted to online distribution, rendering physical media like floppy disks and cover disks a nostalgic memory.
A non-playable demo, also known as a rolling demo, displays a recording of gameplay to show off features without allowing user interaction. In contrast, playable demos are stripped-down versions of the full game that restrict gameplay to some levels, features, or time limits.
Demos of adventure games are often limited to a very small number of rooms and have the save game feature disabled to force players to experience the narrative in a linear fashion. This design choice ensures players cannot return to previous points within the trial version.
Shareware allows players to upgrade to the full version by adding other episodes while leaving existing files intact, whereas demos are self-contained programs that cannot be upgraded. This distinction meant players could retain saved games on the shareware version of Descent but not on the demo version of Descent II.