What is the difference between binary form and rounded binary form?

Binary form and rounded binary form are mostly the same in that they both have two related themes, one in each section, A and B, modulate to the dominant at the end of the A section, and back to the tonic at the end of the B section. The A and B sections are both repeated in binary and rounded binary form. The difference is, however, that in rounded binary, the theme from the A section comes back at the end of the B section, slightly altered. Therefore the form for binary is simply A:B, whereas for rounded binary it is A:B(A').