It is used to describe the container of something, similar to the English phrase "a box of" or "a can of".
Here are some examples:
* Boîte de conserve: Can of preserves
* Boîte de chocolat: Box of chocolates
* Boîte de médicaments: Box of medicine
* Boîte de sardines: Can of sardines
* Boîte de peinture: Can of paint
It's important to note that "boîte" can also mean "box" on its own, without the "de". For example:
* La boîte à musique: The music box
So, the meaning of "boîte" depends on the context and if it is used with "de" or not.