Complex sentence: If the two phases are at the same initial pressure, there is osmosis or transfer of solvent across the membrane into the solution, until equilibrium is attained when the pressure difference equals the osmotic pressure.
Split into simpler sentences: If the two phases are at the same initial pressure, there is a net transfer of solvent across the membrane into the solution known as osmosis. The process stops and equilibrium is attained when the pressure difference equals the osmotic pressure.