The process of uncovering a problem that is shared across a group of prospective customers. Usually done when you're trying to figure out if a product idea has any legs
Usually make contact via email or Linkedin. Show your cards up front and make it clear that you're not selling anything, just looking to learn more about a specific problem you think they have. Set expectations that convo will be brief (<20 minutes).
If someone has a real problem, they will be actively looking for solutions and would be happy to chat with you.