What is the difference between PoE and Passive PoE?

The general meaning of Power over Ethernet (PoE) is the capability of passing electrical power along with a data signal over the same Ethernet cable. This can be a pretty useful arrangement, since it requires only a single cable to provide both the electrical power and the data to receptors like Access Points (APs) and devices like IP cameras. The power signal can be carried on an entirely different conductor within the Ethernet cable,  or it can be carried on the very same conductor as the data signal.

Source: Blog.T3innovation.com