How PUC works
PUC stands for Pre-University Course. It is what Karnataka calls Classes 11 and 12, run by the Department of Pre-University Education. First year is 1st PUC, second year is 2nd PUC. Elsewhere in India the same two years are called Class 11 and 12, or Intermediate, or Plus Two — if you read a national website, those words mean PUC.
You choose a stream — Science, Commerce or Arts — and within it a combination of subjects. The combination is the thing that matters, because it decides which entrance exams you are permitted to sit two years later.
Your 2nd PUC marks matter in two separate ways, and families often confuse them. They decide whether you pass and are eligible, and for some courses they contribute to the admission rank. But for most professional courses — medicine, engineering, and others — a separate entrance exam decides your seat, not your board marks.