When I get up in the morning and make my way to my office, I sit down at my computer, and type in a password. Few other people actually come into my office, so having a password seems a tad unnecessary. However, I keep it there just in case someone does happen to come in with malicious intent. But soon, I might not have to worry about typing in a password anymore, as Windows will already know that it's me sitting down.
While it would be nice for my computer to know it's me without any external input, Windows does still need some help. The help comes in the form of an app, which you'll install on your phone. It will connect to your computer via Bluetooth, and when you're in range of your computer, you can pull out your phone and tap on the icon of the computer you're logging into.
Since I usually already have my phone out as I'm heading into the office, a few extra taps would generally be easier than typing in the 10 or so characters that I tend to use on my machine. Of course, if you leave your phone in the other room, you can still type things out the old-fashioned way.
If you want to try this out for yourself, you can. There is currently an app available on the Windows store for your phone. Unfortunately, its a beta version of Microsoft's Authenticator app, which is only available on Windows phones. You'll also need to be running Windows 10 on your PC to try it out. So for the few hundred people that actually have Windows phones (nothing against Windows phones, they just have a very poor market share), this might be worth checking out.
Source: Microsoft Store