A solution is a value that satisfies an equation, makes it true. For example, the equation x+1=4 has the solution x=3, since 3 is the only value for x that makes the equation true. The solution set for an equation can be everything from zero to infinitely many. The equation x=x+1 has zero solutions since it's impossible to add 1 to a value and get the value itself. An equation can also have infinitely many solutions, like x+x=2x. It is possible to enter any value for x and the equation will be true.