A philologist is a type of linguist, though the exact meaning of the term has changed over the years. Philology literally means "love of words," and the field often deals with literature more than other branches of linguistics do. In the modern academic world, the term is usually understood to mean the study of written texts, usually ancient ones.
It was much more common in the 19th century than it is today for a linguist to be called a philologist. Philology was the precursor to today's linguistics, which has changed to favor spoken data over written data. Comparative and historical linguistics, in which words from different languages are compared and contrasted to determine the current or historical relationships between languages, have their roots in the 19th century field.
In an earlier era, this person focused his or her study on language as it pertains to literature and culture. Individual words, their history, and the common history of words in different languages were also of interest. Literary interpretations and the study of language went hand in hand; in this respect, the modern field of comparative literature can also be seen as having its roots in philology.
Today, the field is no longer concerned with literary interpretation but is instead concerned with deciphering texts and understanding language through texts — not understanding literary texts through language. A philologist may work with little understood languages that are no longer spoken, such as when a textual record is all that is known of the language.
The modern methods of philology also began in the 19th century, notably with the deciphering of the Rosetta Stone in 1822, which paved the way for the translation of Ancient Egyptian hieroglyphics. Deciphering ancient texts is complicated by the poor physical quality of many records and the lack of consistency in the spelling and writing styles of many ancient authors and scribes. Work is ongoing on some writing systems, such as those of the ancient Mayans and the Etruscans, and some, like the notorious Linear A of the ancient Minoans, remain a complete mystery.