Gen IV Locations
Each location may also have extra information associated with it. First, if you're not sure how to access the area you're looking at, there's "Where", which describes in various unnecessary detail exactly where it is, how to get to the different sections and where you actually find the wild Pokémon, unless I was too lazy to describe it or deemed it too obvious. Some locations will also have "Notes", which is where I list any special Pokémon that appear there (such as the changing Pokémon in the Great Marsh or the Trophy Garden and any interactable legendaries such as Heatran in Stark Mountain or Articuno in Seafoam Islands) and any other nonobvious tidbits about the Pokémon in this location; I'd recommend always taking a look at the Notes if they're there. Finally, the more complex tables will have "How to read this table", a brief explanation of what the information given in the table actually means in case you find it confusing.
For these same more complex tables, there will also be another form on the right to simplify it. Simply select the conditions that apply to your game and press the Refresh Table View button to hide all the rows that don't actually apply for you right now and recalculate the Statistics portion, which otherwise just assumes that every possibility under each condition is equally likely.