There are different versions of the Raspberry Pi.
Details can be found on https://en.wikipedia.org/wiki/Raspberry_Pi.
The three different ARM architectures can use the same binaries.

Raspberry Pi 1
 - Model A   ARMv6, 256 MB, no ethernet, 2 USB ports
 - Model A+  ARMv6, 512 MB, no ethernet, 2 USB ports
 - Model B   ARMv6, 512 MB, 2 USB ports
 - Model B+  ARMv6, 512 MB, 4 USB ports

Raspberry Pi 2
 - Model B   ARMv7, 1 GB, 4 USB ports

Raspberry Pi 3
 - Model B   ARMv8, 1 GB, 4 USB ports (uname reports armv7l when running in 32-bit mode)

