These three work like SUM: give them a range and they return one number.
=AVERAGE(B2:B9) adds the numbers and divides by how many there are.=MIN(B2:B9) returns the smallest number.=MAX(B2:B9) returns the largest number.
All three skip empty cells and text. That matters for AVERAGE: a blank cell is left out, but a cell holding 0 counts. If a score is missing, AVERAGE divides by the scores that are there, which is usually what you want. Dividing a SUM by a fixed count would treat the blank as a zero.
You can combine them with arithmetic, for example =MAX(B2:B9)-MIN(B2:B9) for the spread between the highest and lowest value.