ive got one scenario can someone explain??

okay, theres a runner at one and two. then batter hits high ball to between 1 and 2. then the runners at one and two forced to run right? but how does double play come in and if the infielder catches the high ball, is it all the runners auto out? or must do that double play thing??

okay, i realise ive learnt vv little in my pri school years of softball. I DONT KNOW WHY. i guess im dumb.