A lead has given contact details; a prospect has been qualified as having the right need, assets and timeline. Prospects convert at 3-5x the rate of raw leads.
Terminology varies, but in a UK IFA firm a useful distinction is: a lead is any person who has provided contact details via an ad or form; a prospect is a lead who has been qualified on need, assets, timeline and suitability. Prospects typically convert to clients at 3-5x the rate of raw leads. Reporting should separate the two at every stage.