The General Certificate of Education Advanced Level (commonly shortened to A-Level) is a set of exams taken worldwide. They are usually taken during the end of secondary school. In the UK, they are usually taken two years after the students have completed GCSE or IGCSE exams.
A-Levels are usually split into six parts, each with its own exam.
Most people study three A-Levels, and one AS-Level. An AS-Level is the first half of an A-Level. An AS-Level can be studied on its own, but to get an A-Level the second half must also be completed. The second half of an A-Level is an A2-Level. A student might opt to appear for his AS (Advanced Subsidiary) and A2 together in one go.
Students need A-Levels if they want to go to university to study for a degree.