FreeBSD runs on many hardware platforms.
If you do not know what you have, you most likely have what FreeBSD calls amd64: a 64-bit processor, usually made by either Intel or AMD.
If you have an older Intel or AMD processor that only supports 32-bit mode, then you have what FreeBSD calls i386.
Both of those platforms are well-supported. The degree of support of the other platforms is explained in detail on each page below.
amd64 -- most workstation and server-class systems
ARM -- Raspberry Pi and similar systems
arm64 -- Pine64 and similar systems
PowerPC including powerpc64