Say I have a dataframe called 'penguins'

I can write code like: penguin_sizes <- select(penguins, weight, height)

Here, weight and height are columns inside the dataframe. But I can refer to them as if they were objects in the environment (I., e without quotes) because the select function looks for them inside the penguins dataframe (it's first argument)

This is a very simple example but it's used extensively in some R paradigms