Definition
A lead that has been engaged by sales and confirmed as a fit for pursuing a deal. Further along the funnel than an MQL; typically has confirmed budget, authority, need, and timeline. The difference from an MQL is who did the confirming: an MQL is inferred from behavior, an SQL is verified in a conversation.
What it looks like in practice
A moving company gets an inquiry about a house move in October. The estimator calls and asks the questions that decide whether this is real: is the closing date set, is it a full-service pack or just loading, is the person on the phone the one paying, have they already had someone else out. The answers come back; date confirmed, both floors packed, she is the decision-maker, and the quoted range doesn't scare her. Now it's worth sending a surveyor and building a detailed quote. Had the date been maybe spring, that same effort would have gone into a guess.
Why it matters
Calling something an SQL is a spending decision. It's the moment a business commits its most expensive resource (a proposal, a site visit, a custom quote, an owner's evening) to one prospect over another. For an owner doing their own selling, the costly mistake is treating a warm but unready inquiry as an SQL and sinking hours into a deal that was never going to close this quarter. Disqualifying early is not lost business; it's time returned to the deals that can close. The honest gut check on budget, authority, need, and timing is what keeps the pipeline forecast worth reading.