The document describes how to define and reference variables and elements in MATLAB. It shows that a variable can be defined as a vector using linspace with a start, end, and number of elements. A variable can also be directly defined as a matrix by listing its row elements. The colon operator : can be used to reference an entire row or column of a matrix, and ranges with 2:3 specify a subset range. Rows and columns can be deleted by setting them equal to an empty array.