An equation is a relationship whose primary use is solving for a value.
An equation makes use of the equality (=) sign.
An example of an equation is x + 6 = 46.
A function is a mathematical machine whose purpose is to transform input variables into output according to the function rule.
A function can be described by an equation, a graph, a program, a table, etc.
An example of a function is y = 2x - 5.