A hot desert is usually the sandy-Egyptian type of desert. The semi-desert looks like a scrubland. The semi-desert is the one you usually see on westerns. Deserts are formed when something gets in the way of rain clouds. This can be caused by winds or mountains.
Some deserts are near oceans.
The Mediterranean Sea is near the Sahara desert. California is another good example of a desert by the sea. Deserts by bodies of water are usually caused by winds. Mountains also play a roll in forming deserts. A good place to find plenty of mountains jumping up in front of innocent clouds is by the Himalayas.