Indian students preparing for Germany routinely prepare for the wrong certificate, and find out at application time. The four names you will meet:
Goethe-Zertifikat (A1–C2). The Goethe-Institut's general CEFR exams. A1 and A2 matter for family and visa purposes; B1 and B2 are widely accepted for pathway and some undergraduate entry, and B2/C1 for many German-taught programmes. Recognised everywhere, available in India.
TestDaF. Designed specifically for university admission, scored in TDN levels 3, 4 and 5 across four skills rather than as a CEFR pass. Most German-taught degrees ask for TDN 4 in all four sections, which sits around B2/C1. If your target is a German-taught degree, this is usually the exam to take.
DSH. Run by the German universities themselves, usually on campus, graded DSH-1 to DSH-3. Accepted by the university that runs it and generally by others, but you normally have to be in Germany to sit it.
telc Deutsch. CEFR exams accepted for many purposes including some university entry; telc Deutsch C1 Hochschule is specifically for higher education.
If your programme is taught in English, you may need none of them — but you will often still need A1 or A2 for a family visa, and B1 is a common requirement for permanent residence later.
What to do, in this order: read the programme page for the exact certificate AND level, check whether all four skills have a minimum (TestDaF TDN 4 in each is different from an overall B2), check the exam is available in your city and how far ahead it books, and only then start preparing. A B2 Goethe certificate is a real achievement and still the wrong document if the university asked for TestDaF 4.