Imagine a beloved candy bar that you buy from day to day at your local brick & mortar shop... Do you know how it got there? Maybe it arrived in a truck from a factory in your country or a container by a ship. Or maybe it was imported via a cargo plane.
And what about the ingredients to produce such a candy bar? They also travelled some distance to the factory by some kind of transportation, which produces additional CO2 emissions into the atmosphere. This co-existing mechanism is what we call a carbon footprint of a product.