Complex sentence: This means that the two bulges of water that travel around the earth are above and below the equator, and some places have one daily diurnal tide, while other places have semi-diurnal tides twice a day.
Split into simpler sentences: This means that if one of the bulges travelling around the earth is above the equator, then the other bulge is below the equator. It also follows that some places will have one daily diurnal tide, while other places will have semi-diurnal tides twice a day.