How does the geography affect the people that live there?
As the previous poster pointed out, geography had a great deal to do with how certain communities developed. Civilizations that developed in places with large, flat and fertile fields were very different from those that developed around a coastal region dependent on fishing or a mountainous region that had to find other ways to supply food, etc. These of course also determined how they built homes and how they interacted with other civilizations.
In a modern developed country like the United States, geography now often plays a role in choices people make about where to live. Boulder, Colorado is very popular amongst people who enjoy hiking in the mountains or riding bikes in the same. Florida is popular among people who want to live near a beach and the ocean. Some of the constraints imposed by geography in the past are no longer as powerful given the construction of transportation and other infrastructure to distribute goods and services regardless of geography.
Geography determines the physical conditions in which one has to live. These conditions include topography, soil type, climate patterns, natural resources, vegetation, ecosystem, etc. Different places have different geographical features and influence the life style and habits of the people residing in that region.
For example, someone living in Hawaii does not have to worry about snowfall or excess cold weather and hence has no need of warm clothes. Compare that to someone residing in Siberia or the Himalayas, where snow is a part of life and warm clothing is part of life. Other examples are the flood-prone parts of India, or hurricane-prone Eastern Seaboard of the US, or earthquake-prone regions of Japan. The type of housing required would be different in all these cases. The type of vegetation that grows in a place is also a function of its geography and determines the food habits of the people residing there.
Many people even base their career choices on their geographical location.