The most common definition of geography is as follows: geography is “the study of the physical features of the earth and its atmosphere, and of human activities as it affects and is affected by these, including the distribution of populations and resources, land use, and industries” (from the Google Dictionary). This is the baseline definition of geography, but the study of mountains, rivers, oceans, and other landmarks could be part of geography.
If you’re talking about a class in geography, you’re probably focusing on the geography of a country or one aspect of the above definition. There are classes that focus on general geography of the world, on the geography of certain countries, and on how other factors affect geography.