Graduate work, like "actual" history, is more focused on primary sources and the creation of of original work.

Depending, of course, of the type of assignments you receive, undergraduate history courses may only require limited (or even no), consultation of primary sources. When requiring people to consult primary sources, the focus might be on teaching the interpretation of sources, or on putting sources in context, with little expectation of originality. You would rarely be expected (or only at a senior level), to conduct sustained research in archives or collections, or to pursue a specific story over a long period of time across multiple sources, or to make an intentionally original argument.

One thing I found absent from my personal experience with undergraduate history: the requirement to justify one's work with reference to the historiography. That is to say, I was never asked to consult existing work on my topic and identify how my work contributes or responds to existing scholarship. In fact, I had never heard the term "historiography" until graduate work, which put me at a distinct disadvantage compared to other better educated, more specialised, colleagues.

Typically, graduate work is much more focused. I was particularly scattered as an undergraduate, taking courses of all different time periods and areas. Even those who focus are likely to still have a relatively broad focus e.g. "medieval history". In a medieval history PhD, your focus would be more focused--women in the 12th century in France, for example. You would certainly read around this subject and would likely identify yourself as a "medieval historian" but would still have aspects of medieval history which you knew less (or even very little) about.