The field of anthropology is usually broken down into four main branches: cultural anthropology, biological anthropology, linguistic anthropology and archaeology. Each separate branch of this discipline seeks to study some aspect of humanity - whether it's culture, language, or human biology and evolution.
Cultural anthropology is generally seen as the widest and most practiced branch in the field and is focused on studying human culture and its effect on both the individual and the society as a whole. Most cultural anthropologists focus on one specific aspect of culture, such as religion or politics. Biological anthropology differs from cultural anthropology in that it looks at the role that genetics, history and evolution have played in making humans and societies into what they are today.
Whereas both cultural and biological anthropology are at least somewhat concerned with modern man, archaeology is only concerned with history and seeks to understand and reconstruct what life was like in past cultures and societies. Archaeologists can be focused on any area of human history, from the pre-human, stone age to more recent times.
Linguistic anthropology is focused solely on language, from how languages work, grow and evolve to the effect language has had on human history and development.