Economic buyer
Can release the funds and give the final yes. Often not the person who started the conversation, and identifying them early is the highest-value qualification step available.
Technical buyer
Evaluates against standards: security, integration, data handling, internal policy. Usually cannot approve a purchase and can very often stop one.
User buyer
Lives with the result every day. Their objections are the most dangerous to dismiss, because unaddressed user resistance turns into non-adoption and then into a cancellation at renewal.
Champion
Advocates internally when you are absent. A real champion gives you access, shares internal context you could not have obtained yourself, and takes action without being prompted.
Procurement and legal
Enter late and control the timeline. They are not usually persuadable on the merits of the product, and their process is the reason verbal agreements take weeks to become signatures.
Detractor or blocker
Opposes, sometimes for reasons entirely unrelated to your product: a competing initiative, a previous poor experience with a similar tool, or loyalty to another supplier.