WTH are R-squared and Adjusted R-squared?

Today I am going to explain the concept of R-squared and adjusted R-squared from the Machine Learning perspective. I'll also show you how to find the R-squared value of your ML model. It acts as an evaluation metric for regression models. To understand it better let me introduce a regression problem. Suppose I'm building a model to predict how many articles I will write in a particular month given the amount of free time I have on that month.