Servo

Servo v4.1, an integrated debug probe. Includes an USB3 hub, Ethernet, CCD and god knows what - except for an actual Servo debug port

Depending on the context, Servo may refer to one of the following:

• Servo v2/Micro/v4/v4.1, google's debug probes. Not available to the general public, neither are the schematics. Most info about them comes from this chromium.googlesource.com page.
• Yoshi Flex Cable, an adapter to connect the Servo v2 to a Servo Debug Port
• Servo Debug port - a proprietary port, exposing several UARTs, SPI, power/reset buttons and several others.

Quite interestingly, despite being still named after the debug port, according to google's public docs modern Servo debug probes seem to no longer include a way to connect to an actual Servo port, instead relegating themselves to USB-C CCD debugging (which can be done equally well with a SuzyQ)

c2d2

In newer boards, google has gotten rid of the Servo debug port due to its footprint. Instead, there's c2d2, an 8pin CCD header.