On real baseball fields there are a number of infield drags each one designed for a different purpose.....
In most HS and youth programs the infield drag can be anything from a real piece of field maintenence equipment to on old bed spring....or a sewer grate....or a section of chain link fence.....
The drag is meant to smooth, level and eliminate the larger debris on the infield....
Just wait until you go to college....not only will you be getting a degree in academics, but in most programs you could qualify for a minor in field maintenece.....
Much of the day to day up keep at a lot of schools is done by the team.....
Oh and the most thorough way to clear the infioeld of rocks I have seen is the coach lines up the whole team on one foul line and have then walk to the other line side by side picking up rocks one by one.........
Nothing like playing (or umpiring) on a well groomed field....
Best of luck...