What is the difference between a bacterium and a rickettsia?

The other day in a microbiology seminar, someone brought up how rickettsiae are technically bacteria but behave very differently. That got me curious, so I dug into it and found that while rickettsiae fall under the bacterial domain, they stand out because of their strict intracellular lifestyle, reliance on vectors like ticks, and reduced metabolism. This post breaks it all down clearly.