texture blending?

Ok, im still jsut getting to grips with terrain generation and textures and im stuck on how i can get the smooth transition between one texture to another?

No “multi texturing” on top of each other.

As in grass blended into the sand? Or stone blended into grass?

My current status is i can texture each poly what ever texture i want, but obviously is very square and “tile” looking?

So just the blending bit im stuck on?