Parenthesis, Exponent, Multiplication, Division, Addition, and Subtraction
What it means is that it's an order of solving equations, for example:
(3+5)^2+6/8
Knowing the first things to do, P, you start off doing the problems in the parenthesis.
(8)^2+6/8
Now exponents.
(64)+6/8
Now division. By the way, if you have a problem like 8/2*6, you can do it left to right, it doesn't matter the order of both the multiplication and division, well if it's in its own equation.
PEMDAS", which is turned into the phrase "Please Excuse My Dear Aunt Sally". It stands for "Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction".