Update README

Author: HarrisonGrodin

README.md

@@ -182,7 +182,13 @@ context-aware single variable of the IR. Its fields are described as follows:
 ### Operations
 
 Operations are the basic composition of variables and puts together the pieces
-with a function. The `~` function denotes equality between the arguments.
+with a function.
+
+### Equations
+
+Equations are stored using the `Equation` datatype. Given expressions for the
+left-hand and right-hand sides, an equation is constructed as `Equation(lhs, rhs)`,
+or equivalently `lhs ~ rhs`.
 
 ### Differentials