One can answer to the question "what is Egyptology?" in one sentence: the study of everything about Ancient Egypt. However, Egyptologists may concentrate on some specific topics, such as warfare, language, art, pyramid-building, religion, food, industry, trade, etc. I, as an Egyptology student, prefer languages to any other components of Ancient Egypt. It is also noted that Ancient Egypt had its history of about 4000 years (from 3500 BC to 300 AD). Of course, the civilisation had changed along with the history.
The important thing which one should realise is any element of one culture could not separate from one another, especially in Ancient Egypt. For example, their language employed the hieroglyphs, the pictorial signs, as the letters. Particular signs like the Ankh, a sign for "life", are used in a picture in order to add some meaning. Also, signs are frequently shown on small objects, statues, and even styles of temples.
The study is supported by a massive amount of both textual and archaeological evidences. The textual evidence includes oracles, inscriptions, reports of battles, lists and receipts of goods in trade, and so on. The archaeological evidence means the founds themselves indicating their materials, techniques, chronologies, and so forth.
Though it is the study of Ancient Egypt, Egyptologists often need to know what happened in other ancient countries. Libya (west from Egypt), Nubia (modern Ethiopia: south from Egypt), and Syria-Palestine (in the Near East) areas are the most frequently mentioned foreigners.
Even with studies done by many scholars for a few hundred years, Egyptology still has a quite large number of themes to tackle.