The difference is that a function shows the relationship between two or more variables and an equation shows the relationship between their two sides.
However functions are equations, it's just written differently. For example:
[tex]\begin{gathered} y+x=5\text{ }\rightarrow\text{ is an equation} \\ y=5-x\text{ }\rightarrow\text{ is a function} \end{gathered}[/tex]Both reprensent the same line and both have the same results for the same x value, but their are written in different forms.
