Most operators are infix operators: they have two operands, a left-hand side (lhs) operand and a right-hand side operand (rhs).
An infix operator can either have whitespace before and after the operator or have no whitespace neither before nor after the operator.
Infix operators have a precedence that indicate how strongly they bind to their operand and a left or right associativity.
A few operators are prefix operators: they only have a right-hand side. Prefix operators are followed immediately by their operand: they cannot be separated by whitespace.
The whitespace rules are necessary to support unambiguous parsing of expressions spanning multiple lines without requiring a separator between expressions
The operator at the root of the parse tree has the lowest precedence.