Output being the thing that they will sell in the market for a price. The production process tells us that a certain amount of labor, natural resources and capital will produce a certain amount of output given the technology available to the firm. The method of combining the different inputs along with the technology to get output is called the production function. It tells us how much output can be produced with different levels of inputs and the given technology. It is essentially a receipt for making output, just like you would bake a cake.
Lets define three terms first.
You have to know the definition of the words in the language we are speaking. Usually we labor is the variable input. The first column is the amount of labor used. Since the factory size is fixed it is not going to change. Total product is the output produced using different amounts of labor.