European Credit Transfer and Accumulation System (ECTS) is part of the European Higher Education Area used for the comparison of study programmes.
The system allows recognition of academic qualifications obtained abroad and periods of study abroad.
It allows you to "measure" on a point scale the amount of work a student must put into a particular subject/class.
As a rule, 30 points are awarded for a semester of study, while 60 points are awarded for a full academic year of study.
More information on the ECTS system here: https://ec.europa.eu/education/resources-and-tools/european-credit-transfer-and-accumulation-system-ects_en