Alice is using the concept of functions. Functions allow a programmer to create a reusable set of instructions. Instead of writing the same code over and over, a function can be defined once and called multiple times whenever the operation is needed. This enhances code readability and maintainability. The other options provided do not directly refer to grouping code for reusability; 'variables' store data values, 'arrays' hold multiple values in a single variable, and 'objects' encapsulate data and behavior but are not specifically for grouping and reusing a set of instructions.