ECTS credits are workload units to build your programme. They reflect the amount of work necessary to pass a particular learning activity (e.g. a course or a seminar) and are calculated taking into account the total time needed in order to achieve the desired learning outcomes, including the time spent in individual study.
Being a standard European measure, ECTS credits will make it easier for your studies at UCL to be recognized by your home university.
A standard academic year is equivalent to 60 ECTS credits. Depending on how long you will stay at UCL, you must therefore, in general, make up a programme of 30 credits (one semester) or 60 credits (two semesters). The exact number of credits you need to take is set by your home university, depending on your individual learning path. However, at UCL you will be expected to make up a programme sufficiently close to the workload of a typical full-time academic semester or year.