Explanation

The x axis represents the real component, and the y axis represents the imaginary component. Complex numbers are numbers with both real and imaginary parts: $$z = a + b\sqrt{-1} = a + bi$$ Reverse Polish Notation, or postfix notation is a way of writing functions. Normally, most people would write functions using infix notation like this: $$a + b + \sin c$$ Postfix notation looks like this: $$a\ b + c \sin +$$ For a more simple example, $a + b$ would be $a\ b\ +$, and $\sin x$ would be $x \sin$. You can plot multiple functions by separating them with commas, but it will be slow.

List of all functions and constants

Function or constant	What it means
x	The input to the function.
i	$i = \sqrt{-1}$
n (e.g. 5, 4, 3.1, -32.123)	A real number.
ni (e.g. 5i, 4i, 3.1i, -32.123i)	$i$ ($\sqrt{-1}$) times a certain real number.
+	Addition
-	Subtraction
*	Multiplication
/	Division
^	Exponentiation ($a^b$)
re	Real component. If $z = a+bi$, $\textrm{Re}(z) = a$
im	Imaginary component. If $z = a+bi$, $\textrm{Im}(z) = b$
pi	$\pi = 3.14159265...$
e	$e = 2.7182818...$
sqrt	$\sqrt{x}$
abs	$|x|$
exp	$e^x$
sin	Sine
cos	Cosine
tan	Tangent
r, theta	Polar coordinates
ln	Natural logarithm ($\log_e x$)
log	Logarithm ($\log_a b$)
sinh	Hyperbolic sine
cosh	Hyperbolic cosine
tanh	Hyperbolic tangent