the earth is finite right...but can you point me out a boundary! 
Yeah, a real definite boudary.
Take an object moving away from the earth at any point and you'll find the boundary pretty quick.
You've learned what a sphere is, congratulations.
The universe is probably infinite in the way in which mass warps space. The earth moves in a straight line around the sun. The space is warped around that sun, which makes the earth's orbit a circle. But, the earth isn't moving in a circle, it's path is a straight line. The Sun's mass has created enough gravity to act upon space enough to move that straight line.
Roll a ball along a sheet on a bed. It will roll straight.
Put a 100 pound ball of lead in the center of the bed and roll a ball. It will now curve towards that ball of lead. If the ball of lead is dense enough, it will warp the space (which is the sheet in this scenario) enough to cause that straight line to form a circle around the lead.
Gravity and friction will work agains the ball, but in space that will be minimal.
There's nothing more annoying to me than people speaking with an understanding of infinity, especially when their understanding is minute enough to believe that a spherical object (earth) doesn't have a boundary.
