GPA (Grade Point Average) is the standard summary metric for academic performance in the United States, Canada, the Philippines and many other countries. Letter grades earned in each course (A, B, C, D, F) are mapped to grade points (typically A=4.0, B=3.0, C=2.0, D=1.0, F=0), then averaged — usually weighted by credit hours.
The "unweighted" GPA caps every course at 4.0 regardless of difficulty. A "weighted" GPA gives Advanced Placement (AP), International Baccalaureate (IB) or Honours courses a bonus (typically +0.5 or +1.0), letting strong students score above 4.0.
To convert a US 4.0 GPA into a percentage, divide by 4.0 and multiply by 100 — though this is a rough mapping. Most American universities and the WES credential evaluation service use a more granular mapping per letter grade (e.g. A = 93-100%, A− = 90-92%, B+ = 87-89%).
Indian engineering colleges that use a 10-point scale sometimes call it GPA but it is properly CGPA / SGPA — confusingly identical in name. When an Indian student applies abroad and is asked for "GPA", they should report whichever metric their transcript explicitly names, with the scale.