Bundle is just a group of SKUs which allows customers to buy them together easier. Bundles don't have inventory or prices for themselves, because once you added a bundle to the cart, it will be just individual SKUs.
Packages, in other hand, have their own inventory and prices. if you add a package into the cart, it will act as one.
One example is you can have a bundle of a phone and a cover, but each has their normal price. If a customer just wants the phone, they can still add that bundle to the cart, then remove the cover and just pay for the phone.
In other hand you can sell "a console and a game" as a package, with a lower price than buying each individually. Customers will not have option to remove the console or the game from the cart.
This is a nice write up to describe bundles and packages: https://world.episerver.com/blogs/Shannon-Gray/Dates/2017/6/episerver-catalog-packages-vs-bundles/
What are bundle and package entries? Documentaion (https://world.episerver.com/documentation/developer-guides/commerce/catalogs/catalog-content/Bundles-and-packages/) does not cover descriptions and overview. Any practical example please.