Many WordPress themes rely on "Excerpts" to show a short summary of your WordPress content.
You'll find an "Excerpts" box on all your WordPress Posts, but you won't find them on Pages. Excerpts on WordPress pages used to be a standard feature, then they were removed in WordPress 3.1.
Fortunately, if you need to use excerpts, it is easy to put the excerpt window back for "Pages". All you need is a single line of code.