yes, there is a big difference between a Phalaenopsis and a Dendrobium ...both in culture and care....even the media mix used
it just so happened that it was called a Dendrobium phalaenopsis.... it is a Dendrobium; not a Phalaenopsis....but the crazy Botanists wanted to confuse you and called it Dendrobium phalaenopsis.
Yes, the blooms on Den-phals resemble Phal blooms somewhat. But they are different types of orchids.
They both can be grown on windowsills tho - the dendrobium wanting a bit more sun. And both like warm temps usually (there are some Phal species that will grow cooler).
Phals are monopodial, growing as a single growth from the plant's crown. Dens are sympodial, with new growths coming from the rhizome.
Phalaenopsis has large flat oval shaped leaves and stays quite low.
Dendrobiums have skinny tall stalks that look sort of like bamboo, with leaves much smaller&narrower than those of phalaenopsis.
Flowers look quite different as well.
Pictures hlep, so google some images and you will tell right away!