There are many, many ways to sell things from your WordPress site, from physical products to digital downloads or access to content. The best solution will depend on your particular circumstance and needs. While WordPress can get quite sophisticated in the ecommerce department, a lot of folks just want to be able to sell a few items quickly and easily using PayPal.
In circumstances like this where the user wants the simplest possible solution and knows they want to use PayPal, a fully featured shopping cart / ecommerce solution such as WooCommerce or Shopp might be overkill. Sometimes simple PayPal buttons will suffice.
So there are 2 primary options I recommend:
1) Generating buy butons directly from PayPal
2) Using a simple plugin to create a very basic shopping cart