Okay kiddo, so bulk purchasing is like buying a lot of things all at once. It's like when we go to the grocery store and we buy one apple, that's buying just one thing. But, if we decide to buy a whole bag of apples then that's buying in bulk.
When we buy in bulk, we usually get a better price than buying just one thing because we're buying so many. For example, if we buy 10 apples at once, then the store might give us a discount because they want us to buy more things.
This is similar to when we go to a party and we need to buy a lot of snacks for all our friends. We could buy each snack one at a time, but that would take a long time and be expensive. So instead, we buy a big bag of chips or cookies, that way we have enough snacks for everyone and it's cheaper.
And that's what bulk purchasing is all about, buying a lot of things all at once to save money and make things easier for us.