What is CSAT?

The full form of CSAT is the Civil Services Aptitude Test. It was introduced in 2011 as a part of the UPSC Civil Services Exam (Preliminary) to test the analytical skills, reasoning ability, and aptitude of IAS aspirants.

While the controversy over the introduction of CSAT, officially known as the General Studies Paper-II, in the UPSC exam, continues,  the Civil Services Aptitude Test will continue to be a part of the UPSC Prelims.

CSAT.

CSAT stands for Civil Services Aptitude Test. It is a part of the UPSC Prelims (Civil Services Exam – Preliminary). However, the Union Public Service Commission (UPSC) refers to the exam as General Studies (GS) Paper – II.
Hence, in the context of UPSC Prelims, GS Paper II refers to the CSAT, while in UPSC Mains, GS Paper II is the Polity (etc.) paper.
Candidates are advised to understand the complete UPSC syllabus and the syllabus of CSAT in UPSC Prelims to avoid confusion.