Full Idea
The general will demands the policy which is equally in everyone's interests. Thus we can think of the general will as the general interest.
Gist of Idea
We can see the 'general will' as what is in the general interest
Source
Jonathan Wolff (An Introduction to Political Philosophy (Rev) [2006], 3 'Rousseau')
Book Reference
Wolff,Jonathan: 'An Introduction to Political Philosophy (Rev)' [OUP 2006], p.79
A Reaction
That seems to assume that the people know what is in their interests. Rousseau's General Will mainly concerns who governs, and their mode of government, but not details of actual policy.