Read More: What are extensions?
The altML Chrome Extension is a program built using HTML, CSS, and JavaScript to interact with the browser. The extension's job is to interact with websites, find images that are missing their alt attributes, and contact the caption server to fill them in.
assets/iconsis where all of the icons for the extension live.popupholds the files that load whenever you click on the icon for the chrome extension. This is where preference options are set.altML-contentScript.jsis the JS injected on every web page. This is where images are scanned and captions are fetched from the server,background.jsthis is an extension file that runs in the background instead of per-page.manifest.jsonis where the extension information for Chrome and the Chrome Web Store is located. This requests permissions from the browser, and tells the browser about extension file locations and options.