I believe squats target the glutes/hamstrings/quads.
Plie squats target the inner thighs.
I've read the key to toning your inner thighs is floorwork with lots of reps. Cathe's PS: Legs & Abs has a killer floorwork section (brings me close to tears).
There was a thread about how much space fat occupies vs. muscle awhile back and that must explain why building muscle by lowerbody work makes thighs appear more toned.