If I estimate an intercept only model in Stata

reg c.y

I get an estimate of a constant that shows the mean of the continuous variable y.

In Stata, it is also possible to have an intercept-only model with an interaction term, e.g.

reg c.y##c.x

Now, y gets estimated by a constant, a coefficient for the effect of c.x, and a coefficient for the effect of c.y#c.x.

I am not sure what to make of this result. Is the constant plus the effect of c.y#c.x the constant that I get if x equals "zero"?
Who could give me a hint? I cannot find any explanation in the manuals.