Co-marketing is kind of like when you and your best friend work together on a project. You both have something cool to offer, so you team up to make it even better.
For grown-ups, co-marketing is when two companies team up to promote each other's stuff. Let's say one company makes really yummy cookies, and the other company makes really cool cups. They decide to work together, so they can sell cookies and cups at the same time.
That way, people who love cookies might buy the new cups too, and people who love cool cups might try the yummy cookies. It's a win-win for both companies, and it helps them reach new customers.
Co-marketing is all about teamwork, and making cool new things by working together.