There are two ways to make money on a regular basis. The first way is to work for yourself, and the second is to work for others.
When you work for others, you exchange your time, energy, skills and knowledge - in short yourself - for money.
When you work for yourself, you produce and sell a product or service. What it means is that you convert your energy, time, skills and knowledge into a product or service and sell that thing rather than yourself for money.
You are able to freeze your time and compact it with other resources such as your energy and skills, multiply them into many parts in the form of products, and sell them over and over.
This also goes for you buying products and selling them. You use your time, skills and network to sell products over and over.
It is much better to sell products than to sell yourself for money.