An equation is an equality which is satisfied by a unique set of values of your variables. You have, after the = sign a fixed value, a fixed result.
For example: the equation 4x-2=0 has zero as result and only x=1/2 as solution; this means that if you substitute the value of x=1/2 in the equation you have the result zero, i.e., the equation is satisfied.
Now, a function is similar, the only difference is that now you can have a lot of results after the = sign and so you can have a lot of solutions.
For example: the function 4x-2=y doesn't have a definite result (as before that was zero) but another variable y, so every time you choose an x you'll get the corresponding value of y that satisfies it.
If you choose:
x=1 -> y=2
x=2 -> y=6
....etc.
If x=1/2 -> y=0 which is the solution that we found before for our specific equation (in which the y was already set as zero)!
So to summarize, an equation has a fixed result (after the = sign) and an unique set of solutions (values of the variables); a function can have a lot of results (possibly oo) and, as a consequence, a lot of solutions.
hope it helps
