An MQL, or marketing qualified lead, is a lead that has shown interest through its own actions — downloading a guide, attending a webinar, requesting a demo — but has not yet been vetted by sales. Marketing considers it qualified; sales has not confirmed it. An SDR typically takes the MQL, reaches out fast, and decides whether it is worth pursuing. If it clears the sales questions, it can become an SQL or a qualified meeting.
In plain English
An MQL is a lead that raised its hand. It did something — clicked, downloaded, requested — that says "maybe interested." But interest is not the same as fit or intent to buy. The MQL is marketing's guess; it becomes real only when sales talks to the person and checks it against the ICP.
Why it matters to you
MQLs are a big part of an SDR's inbound queue, and speed decides how many turn into anything. A lead contacted within minutes is far more likely to respond than one reached days later. Know what counts as an MQL at your company, chase the ones that fit the ICP, and treat the ones that do not as a signal to clean up your list rather than a personal failure.