The Octojam is all about writing software for the Chip-8 platform. You can use any tools you like to prepare a Chip-8 ROM, but Octo is a convenient tool for writing and testing such programs.
Octo can save a standalone .HTML document which bundles the Chip-8 ROM together with an emulator. You can then use this .HTML document on Itch to let others play your game directly in their web browser. Here's an example of a game I've published in the past using this method: https://internet-janitor.itch.io/expedition
You can additionally distribute the bare .ch8 ROM as a download on your game's submission page, for use with other Chip-8 emulators.
Does that make more sense?