MQL vs SQL, explained
A marketing qualified lead (MQL) is a lead that marketing judges ready for more attention, usually because of who they are and what they have done: the right city or company size, a detailed form, a pricing page visit, a reply to a campaign. A sales qualified lead (SQL) is a lead a salesperson has spoken to and confirmed has a real need, a budget and a timeline worth pursuing.
The distinction matters because it sets the hand-off. Marketing is measured on producing leads that sales accepts, and sales is measured on turning accepted leads into deals. When the line between the two is vague, marketing sends everything and sales ignores half of it, or sales complains about lead quality without saying what a good lead looks like.
Write both definitions down in plain criteria, agree them between the teams, and record the stage on the lead itself so it can be reported on. Lead scoring helps with the MQL side, because points for fit and intent make the threshold visible; qualification questions such as budget, authority, need and timing decide the SQL side.