How much is 1K pixels?

Excuse me, as a cryptocurrency and finance practitioner, I realize this question may seem a bit out of my usual domain, but I'm curious about something I've encountered in digital design. Could you clarify for me, in layman's terms, what is meant by "1K pixels"? Is it a specific measurement of image resolution? If so, how does it compare to other common resolutions like 2K, 4K, or HD? I'm trying to understand how these pixel measurements translate into visual clarity and quality when dealing with digital media. Any insight you could provide would be greatly appreciated.