In modern networking, there are multiple media types including various types of Ethernet, Fiber Optic and Coax cabling.  The Small Form Factor (SFP) transceiver is a standards-based device that is used to allow different physical network media connections to network devices such as switches.  SFP has a standard mechanical and electrical interface for interchangeably.

Many applications of the SFP are for fiber-optic network connections that provide electrical separation or long distance transmission needs. In most home networking situations, we do not see any use of SFP devices.   There is a growing use case for fiber-optic networking cabling to provide electrical noise isolation.  I will expand on this in a later blog post.

For reference here is the Wikipedia entry for SFP:

https://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver