Especially as smartphone prices continue to rise, you can save a considerable amount of money by purchasing one that's not brand-new. However, not all used devices are the same. Two similar-looking phones might appear at the same price but with different labels, such as "pre-owned," "refurbished" or "certified pre-owned." These each carry different levels of reassurance about what happened before you encountered them.
Broadly, the core difference is that "pre-owned" (or "used") is a description of the phone's history, while "refurbished" describes a process the phone has undergone. A refurbished device has usually been inspected, cleaned and tested, then repaired or fitted with replacement parts as necessary. A regular pre-owned phone, in contrast, is generally sold as-is. Thus, all refurbished phones are used, but not all used phones are refurbished.
This doesn't necessarily mean refurbished is the better option. A used phone with buyer protection, a known history or remaining coverage can be just as sensible, and sometimes cheaper, than a good refurb. For the least hassle, a reputable refurb is usually the easier choice. However, if getting the most for your money matters more, a thoroughly researched used phone is worth considering.