If you are a user of the Google Chrome web browser, you may have read here on the site or elsewhere that Google plans to introduce changes in regards to extension installations for Chrome Stable and Beta versions that run on Windows systems.
It means basically that Chrome Stable or Beta users who run Windows can only install extensions that have been uploaded by their authors to the Chrome Web Store.
It does not matter if those extensions are listed visibly on the store, or if the author has selected to hide them instead.
Anyway, there are ways around those restrictions as outlined in the linked article at the top.
Using the Chrome Web Store exclusively means that extensions can only be installed directly, but not downloaded anymore, at least not without third-party aid.
The reason here is that Google does not display download links at all. This makes it difficult to install extensions on a computer that is not connected to the Internet at all or all the time, and also to backup extensions in case it gets pulled from the store by Google or the extension developer.
Chrome Extension Downloader is a browser extension for Google Chrome that you can install to add download options to the Chrome Web Store.
The extension adds two download options to every extension page on the Chrome Web Store. You can either right-click the "installation button" on the page and select the Download Chrome Extension option from the context menu, or left-click on the icon that the extension adds to the browser's address bar when you are on a Chrome Web Store page.
Side-tip: You can download these extensions as well to install them in the Opera web browser, as most Chrome extensions are also compatible with it (or use Opera's official Chrome Extension Download addon instead).
A click on either link opens a new page that initiates a save file dialog right away to download the crx file to your local system. Note that this takes place on a third-party site that is not maintained by Google.
It is interesting to note that you can use the service without installing the extension in Chrome. Just head over to the official website and paste the web store url of the extension or the extension ID into the form on it.
You end up with a crx file that you can drag and drop to the chrome://extensions/ page in the browser to install it.
If you need to download extensions regularly from Chrome's Web Store, then you may want to consider installing the Chrome extension to do so. If you do so only occasionally, it is probably better to use the web service instead as you do not have to install another extension for that purpose then.