I need help to understand some Data Science Foundations

I’m doing Codecademy’s DATA SCIENCE FOUNDATIONS II. In the Exploratory data analysis I dont get some concepts. Like how do I know wen variables are associated??

In this link have an exercise to put in practice what we learned, I did the plots and calculations, but the questions they asked me I DONT KNOW WHAT TO ANSWER!

The Task 2, we have to calculated the mean difference, but they asked if the variables are associated.

The Task 3, We need to create a set of overlapping histograms that can be used to compare the points, than comes the question: Do the distributions appear to be the same?

and go on… Please someone answer this exercise and help me with the knowledge.