What is Routine?
Routine is a pre-defined Workout which contains all the pre-defined exercies (including reps & weight). After you setup this once, you can start your trianing by just a simple click, and every pre-defined exercies will be there.
For normal use cases, people setup their own training goals first and then break them into different routines so they can train each part separately (for example, leg day, chest day ... etc) on different days.
You can customize your routine to fit your training goals and the only limitation is your imagination :)