From wikipedia (https://en.wikipedia.org/wiki/Automatic_link_establishment):
"[ALE is] the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system that enables the radio station to make contact, or initiate a circuit, between itself and another HF radio station or network of stations. The purpose is to provide a reliable rapid method of calling and connecting during constantly changing HF ionospheric propagation, reception interference, and shared spectrum use of busy or congested HF channels."
That said, the rest of the site is worth browsing. I see it appear here on HN every so often, and it's a neat dive.
As an aside, I met the page's maintainer, Albert LaFrance, in an IT security course in college. Cool guy. He told me he got interested after wondering what the large microwave relay tower that used to be in Tyson's Corner, VA was used for. He started collecting information and inviting contributions after that.