Based on the documentation, it'll use Machine Learning to improve connectivity and performance --> so is this going to switch Salesforce login by default to Edge?
Salesforce could have done a better job explaining this (and picking a less problematic way to brand it). From the comments, it's worth noting that this will be enabled for everyone using "My Domain" on 2020-07-13, and you are being given the option to enable it early.
When talking about "Edge" and web stuff, I wouldn't blame people for thinking they're talking about Microsoft's Edge browser, but that's not what they're talking about.
For people who have some networking experience (as in computer networks), "edge" has a different meaning1. Salesforce isn't really talking about this either though.
Quoting from that help page
What is Salesforce Edge?
Salesforce Edge delivers an enhanced user experience, consistent quality content delivery, and improved download times for users from across the globe. It does this by redirecting requests to the closest Salesforce location where Salesforce Edge is deployed. It provides a range of services that include TLS termination, Static Caching, and TCP optimizations. The application delivers data using the Salesforce infrastructure which protects, uses, and processes data appropriately and in accordance with the law. With Salesforce Edge, you can continue to get the same trusted infrastructure while also receiving these improved benefits.
In normal human language
To put it in more standard words, Salesforce is deploying their own CDN (content delivery network) with special A.I. sauce to cash in on a tired buzzword. This goes beyond the normal region-based datacenter thing they've been doing for years. If you have myDomain enabled, it'll try to serve your requests from the nearest CDN node. This should make things faster2
1: An "edge" device is one that sits at the edge of a network (as opposed to a core or access device). An edge device is generally one that will end up talking to devices outside of your own network. If you have a wifi router in your home that needs to be connected to a modem, that modem would be an "edge" device (not 100% accurate, but good enough for us). 2: By "faster", I mostly mean lower latency (the time between when you make a request, and when data first starts showing up). You may or may not notice requests completing faster, because that depends on how fast each network segment between you and Salesforce is (including the download speed you get from your ISP). Latency can be a factor if multiple requests are being made (which is likely the case).
You should keep in mind that the TLS connection will be terminated at the nearest data center based on your location. After this the payload is encrypted again and will be redirected to your destination data center. That means you lose the end-to-end encryption! It's very strange: On https://help.salesforce.com/articleView?id=000350511&language=en_US&type=1&mode=1 it is written: "Public Cloud and Salesforce Government Cloud orgs are currently excluded from the move to Salesforce Edge.". So you can ask yourself: Why?!