Visitor
Also known as: Traffic
A visitor is somebody who came to look. They have not bought anything yet.
Ten people walked past your stand today and stopped to look at the sign. That is ten visitors.
None of them bought lemonade. They just looked. That is allowed.
Visitors are not the same as money, but you cannot get money without them. Nobody has ever bought lemonade from a stand they never walked past.
Color this: draw ten people looking at your stand. Now color in the three who decided to buy a cup.
For the grown-up holding the crayon box:
Traffic is not revenue, and the gap between the two is the entire subject of conversion. Ten looking and three buying is a rate, and a child who colors that picture has met the concept years before they meet the word.