Ribbon microphones are a type of dynamic microphone with an especially low-mass moving element. Back in the 1920s, 30s and 40s, before European-made condenser microphones were readily available in the U.S., they were the most high-fidelity type of microphone over here (e.g. the RCA brand). The fundamental type of ribbon microphone is inherently bidirectional (a figure-8, in other words), though they can be made to have other patterns via acoustical trickery.
They're not condenser mikes, so the only ones that need external powering are the ones with built-in step-up amplifiers. Those can be useful, though, because ribbons are a whole lot less sensitive than condensers (like maybe 20 dB on average), and they can also have somewhat special loading requirements. You definitely wouldn't use the line inputs on a recorder for them! Also, the actual output voltage of the ribbon itself is absolutely miniscule, and only gets up as far as it does because the microphone has an output transformer. But whenever a transformer steps up voltage, it also steps up impedance, and that can make the mike sound different (especially loss of bass) depending on the input impedance of whatever it's connected to. To avoid that problem, the input impedance of the preamp or recorder should be distinctly higher than the typical 1 kOhm required by condenser microphones.
Ribbons are more fragile than condensers or moving-coil dynamics--much more fragile where wind and other forms of moving air are concerned. You don't even want to walk quickly while carrying a ribbon microphone that's out of its case. And one moron blowing into the mike to see if it's "on" will ruin it.
Finally, ribbon microphones can have very good midrange and/or low-frequency response, but they never have full response up to 20 or even 16 kHz; a lot of them struggle to reach 12 kHz. Most of the affordable ribbon mikes from China start rolling off around 8 kHz or even a bit lower. This can give them an appealing "retro" sound, suitable for an old-timey effect, but that gets old pretty soon.
One type of ribbon that I've used for classical music recording is the Royer SF-1 (single mike, no longer made) or its Blumlein stereo counterpart, the SF-12. That's an American manufacturer that supports their stuff and their customers. And if you use ribbon mikes with any regularity in the real world, you WILL need the support, because the ribbons will need to be checked and replaced now and then, even if you put a lot of effort into protecting them. (Any used ribbon microphone on eBay, for example, should automatically be assumed to need ribbon replacement.)
Another brand that I've used is Beyer--the M 160 supercardioid (there is also an M 130 figure-8). Or actually I should say that I tried to use them, since there was a severe RFI problem at the location. And whenever microphones put out such weak signals, they are far more vulnerable to all kinds of interference. Again that could be an argument in favor of having built-in amplifiers.
--best regards