A 80 is a B- and is one percentage point above a C+. 80 is the lowest percent grade in the "B" letter range.
Aside from 80 out of 100, there are numerous ways students can end up with 80% grades. Here are scales for common number of test questions that can lead to a 80 grade.
Earning test and assignment grades in the 80% range puts you on a path towards getting into many colleges, but scores like this are on the low side. Check out the full discussion on 2.7 GPA to compare your grades, or jump right to the list of colleges you can start thinking about.
Reference table of the percentage grade scale with letter grade and unweighted GPA point equivalents. This grade scale is used my most U.S. middle schools, high schools and colleges.