What is an SQL?

An SQL falls within one of the later stages of the buyer journey. They are ready to contact sales and therefore to start buying something!

An SQL, or Sales Qualified Lead, is someone who is in the decision stage of the purchasing process. It is already clear what the problem/challenge is, the solutions have already been identified and the lead is ready to take the plunge. This is when the lead goes from MQL to SQL and thus from the marketing department over to the sales team. The sales department can then guide this person through the purchasing process, ultimately bringing in a new customer for the company. 

SQL pyramid

A SQL eventually becomes a prospect, if he/she has contacted the sales department and shown interest and interaction. Then it's up to the sales team to close the deal!