The definition you always hear is that marketing creates interest and sales closes the deal. That is true and useless, because it does not tell you the only thing you need: where exactly the handover happens, and who owns what on either side of it.
So here is one example from beginning to end instead of a definition. A company sells accounting software to small firms, and the price is set on a call rather than published on the site.
The example, step by step
Mona runs an office with twelve staff. Her problem is that invoices go out late and she does not know why. She has not thought about accounting software at all.
She reads a post about why invoicing slips in small offices. That reading is marketing: somebody reached her at a moment when she had the problem and no name for the solution.
She comes back two weeks later, downloads a guide on organising the billing cycle, and leaves her email. Still marketing, but now there is a name and an address attached. That moment is the lead.
Somebody calls her. That call is sales: it asks about her size, her current system and her budget, and decides whether this is a fit at all.
She sees a demo, asks about price, negotiates, signs. All of that is sales.
The handover happened at the email. And that is where about ninety per cent of the argument between the two functions lives.
Even the tools draw this line
If that sounds theoretical, take something concrete: the measurement platforms themselves separate the two stages with different event names.
Google Analytics documentation on recommended events lists the lead lifecycle as five distinct events: generate_lead when someone submits a form or their information, qualify_lead when they are marked as fitting the criteria, working_lead when they contact or are contacted by a representative, close_convert_lead when they become a customer, and close_unconvert_lead when they are marked as not converting.
Look carefully at that order. The first event is marketing. The third and fourth are plainly sales. The second one, qualification, is the disputed border, and that is precisely why it exists as a separate event: so it can be measured, because it gets argued about.
The practical consequence: if you measure a single event called conversion, you cannot tell where your problem is. A campaign producing many leads that never close has a completely different illness from one producing few leads.
The real argument, and there is only one
Every marketing and sales disagreement in almost any small company is a version of two sentences: the leads are bad, and the leads are fine but nobody is calling them.
Both can be true at the same time, and there is no way to know without one thing: a written, agreed definition of what a qualified lead is. Written down literally, not understood implicitly.
That definition has to contain things a third person could verify: company size, budget, the decision maker present in the conversation, a timeframe. If it is not checkable, the argument continues.
One thing that makes both work
The best fix I have seen for this relationship is very cheap: whoever owns marketing sits in on five sales calls a month, silently.
What follows is repetitive to the point of comedy. They hear the real objections instead of imagining them, discover that half of what they write answers questions nobody asks, and go back and change the message without being told to.
It works in reverse too. A salesperson who can see where a lead came from and what they read before the call stops starting every conversation from zero.
In a small company both are one person
In most businesses reading this there are no two teams. There is an owner, doing both.
That does not remove the distinction, it makes it more dangerous, because one person drifts toward whichever half they enjoy. Someone who likes selling keeps chasing customers personally and builds nothing that works without them, hitting a ceiling made of hours in the day. Someone who likes marketing keeps producing content and does not follow up with the people who are already interested.
The easiest test: look at last week and split the hours between the two. If either is close to zero, that is avoidance rather than specialisation. The first practical step is making the offer itself clear, which I covered in how to build a strong offer, and the full path in what is the customer journey.
If you are at the stage where everything depends on you personally, there is another version of the same problem in what actually brought you the most customers.
The part people call B2B
The longer and more expensive the sale, the clearer and more important this line becomes, because many stages happen between the two that marketing never sees.
If that is your situation, the team at BDG Labs have written a practical guide to building the second half of this line in how to build a B2B sales pipeline you can actually forecast.
Limits of all this
First: the example above is a sale made on a call. If you sell entirely online with nobody speaking, the line moves toward marketing and qualification happens through the price itself rather than a conversation.
Second: the event names above are Google Analytics recommended events, which are recommendations rather than law. Plenty of companies name their stages differently and there is nothing wrong with that. What is wrong is not naming them at all.
Third: I have not said who should own the final number, because the answer varies. What I am sure of is that when both own the same number with no written definition of the handover point, nobody owns it.