An AISHE code is an ID number used in the All India Survey on Higher Education. Universities start with U-, colleges with C- and standalone institutions with S-. You can look it up in the AISHE institution directory.
Scholarship forms on the National Scholarship Portal often ask for it. Verify Campus shows the AISHE code on university reports where it is known.
What this does not prove: an AISHE code does not show that a university is recognised, that a college is currently affiliated, or that a course is approved. Check those separately.