The types of machines commonly used to help those suffering from paralysis or other disabilities generally rely on some form of hand, cheek, or eye movement. That's the tech that allows guys like Stephen Hawking to speak, write, give lectures, or surf the Internet, among other things. Devices that use a brain-machine interface, on the other hand, "translat[e] neural activity into control signals for assistive communication devices," according to Stanford's report published in the academic journal eLife. It reads your mind and lets you select letters to type.
If you've ever used a TV remote (here's lookin' at you, Vizio) or video game directional pad to manually sift through an onscreen QWERTY keyboard and select individual letters one at a time, this process might look familiar to you. It's cumbersome and frustrating to use, but for this technology, it's the fastest method we've come up with yet. Here's a video that shows how the tech works.