External radiotherapy is normally given as a number of short, daily treatments in the radiotherapy department. It is given using equipment similar to a large x-ray machine. Several different types of radiotherapy machines are used to give radiotherapy, but they all work in a similar way. One commonly used machine is called a linear accelerator (LINAC).
You usually have external radiotherapy as an outpatient. How many treatments you have will depend on the aim of the treatment.