tinyE: What is a "crypto miner"?
I'm going to assume this question is related to the shortage/price of video cards. "Crypto" means a cryptocurrency, such as Bitcoin. Cryptocurrencies are created by running a specific set of mathematical calculations, looking for a value that "solves" the calculations in a specific way. This is referred to as "mining." When such a value is found, that's a "coin" which can then be traded to other users in exchange for goods and services (if the other user is a merchant who accepts that cryptocurrency) or for other currencies, including real world money. The values that constitute coins are quite rare and thus generally require doing a huge amount of mathematical calculations to find.
As it turns out, those mathematical calculations happen to be similar to some of calculations used in creating 3D graphics, and modern graphics cards are basically little supercomputers with hundreds of little calculating engines that can run simultaneously. So for the last several years people hoping to "mine" Bitcoins and other cryptocurrencies have been buying video cards, and since they're not actually trying to display the output of all those calculations on a screen they can put as many cards in a single computer as that computer can support in terms of electricity and cooling. And if they're serious about it, and can afford it, they may well be running multiple computers with multiple cards each. So with these folks buying as many cards as they can get their hands on, per the law of supply and demand the price of video cards has been very high.
So depending on the context the phrase "crypto miner" might refer to either a person running one or more computers that are working on those calculations ("I can't find the new video card I want in stock anywhere because the damn crypto miners have bought them all out"), a computer equipped with one or more video cards being used for those calculations ("I was shocked when I got a $300 electric bill, until I discovered my housemate's cryptominer hidden in the garage"), or the software that runs on computers and uses video cards to do the calculations ("I installed a crypto miner on my computer but I uninstalled it after just a couple of days because I couldn't deal with the noise of the fans running full speed all the time").