The boards that people reach for when they roll their first projects, the hardware that ends up in early prototypes and one-off devices, the hardware that gets targeted by open source projects. The chips that return more than a "databrief" 8 pages long and a single page on a vendor site inviting you to visit the snake pit with "contact sales for more information". The boards you can actually buy with a fixed price tag and a delivery to door, and can find writeups on how to use them for specific things.
If you know what "FAE" is, let alone can get into a meeting with one, you're deep in the trenches, and are pretty much expected to wrangle an extremely poorly documented MCU core that happens to be shipped in a SoC as an afterthought into submission.