Graduate Management Admission Test (GMAT) is a computer adaptive test (CAT) intended to assess certain analytical, writing, quantitative, verbal, and reading skills in written English for use in admission to a graduate management program, such as an MBA

Yes definitely GPA is Important for GMAT, Top schools can be as inflexible on GPA as they are on the GMAT, and one doesn't necessarily make up for the other, although if you have a low GPA, you might be able to explain it with stories, whereas for the GMAT there's not really any explaining you can do.

Exam info:
Type Computer-based standardized test
Developer / administrator Graduate Management Admission Council
Knowledge / skills tested Quantitative reasoning, verbal reasoning, integrated reasoning, analytical writing.
Purpose Admissions in graduate management programs of business schools.
Year started 1953
Duration 3.5 hours
Score / grade range Quantitative section: 0 to 60, in 1 point increments (only 6 to 51 reported),
Verbal section: 0 to 51, in 1 point increments (only 6 to 51 reported),
Integrated reasoning section: 1 to 8, in 1 point increments,
Analytical writing assessment: 0.0 to 6.0, in 0.5 point increments.
Total score: 200 to 800.
Score / grade validity 5 Years
Offered Multiple times a year.
Countries / regions 600 test centers in 114 countries.
Languages English