How do the three branches of government keep each other in line?

Which branch has the power to approve Presidential nominations, control the budget, and can impeach the President and remove him or her from office?

Which branch creates laws?

Which branch is Congress in?

Which branch can veto laws?

Which branch nominates supreme court justices?

Which branch can make sure a law is constitutional?

The executive branch may command the army, but what branch approves military funds?