What is anthropology?

Anthropology is the study of mankind. It's focus is the entire sum of the human experience, from culture to biology, from history to language. There are four disciplines within anthropology:

Biological Anthropology - Studies the biology of humans. This includes the structure of the human body (morphology) and how it varies throughout all humans. It also includes evolutionary theory and dabbles in primatology (the study of primates).
Cultural Anthropology - Studies the full spectrum of the ways in which humans live. It focuses on cultural beliefs (known as world views) and practices. It seeks to describe all human culture in a systematic manner.
Archaeology - Studies the history of mankind (more or less). Focuses on discovering the ways in which peoples in the past lived, and works to reconstruct human history through an exploration of the stuff humans leave behind. This stuff can include anything from garbage dumps to burial sites.
Linguistics - Studies all aspects of human language. It focuses on both the neurological origin and functioning of language, and how language is actually used within a society. There is also a field of linguistics (called historical linguistics) that focuses on dead languages (languages that are no longer spoken) and the ways in which languages change.