These charts show the most efficient ways to obtain a certain enchantment. For this page I will use Smite II as an example enchantment.
The Smite II chart begins with a table of contents listing each kind of item that can have Smite II applied to it. Since Smite II is a weapon enchantment, this is just a list of all types of sword. Clicking on "Iron Sword", for example, will jump to information on the most efficient way of getting the Smite II enchantment on an Iron Sword.
Next there is a summary of the best ways to get Smite II on any type of item. Each row contains information on a particular enchanting option. For example, from the first table on the Smite II page:
|Item||Material||Level||Prob.||XP Cost||Item Cost|
What does this all mean? Well, the first row has information about the efficiency of enchanting Gold Swords, using level 1 enchantments. The probability of getting Smite II when performing such an enchantment is 8.7%.
The two Cost columns are a bit more complicated. The Item Cost for Gold Sword, level 1, says 11.4. This means that if you enchant gold swords over and over until you get one with Smite II, on average you will end up enchanting a total of 11.4 swords (so smaller numbers indicate fewer wasted items). If you are mainly limited by the number of items you can produce (such as if you are enchanting diamond items), this is the column you should care about more.
The XP cost is the expected total amount of XP you will spend if you use this option. (For reference, one hostile mob kill gives 5 XP.) For level 1 enchantments, this is always 7 times the item cost, but for higher level enchantments it can be much larger. See the XP spending page for more information on XP and enchanting.
Now we can also read the row for Stone Sword, level 11. The probability column says the probability of getting Smite II on each sword is 15.2%. Since the probability for each sword is higher, the number of swords you will have to enchant is lower (6.6 instead of 11.4). However, because the enchantment you would be using is level 11 instead of level 1, the total XP you would spend is much higher.
Now, if you've looked at the Smite II page, you know there are four similar looking tables at the top of the page. These are divided into two sections. The first two tables show information on options that have the lowest XP Cost, and the other two show information on the lowest Item Cost.
In each set of tables, there is one labeled "Local Minima" and another labeled "Other good values". The Local Minima table shows options where the relevant cost is at a local minimum. That is, it shows points where either increasing or decreasing the level by 1 will result in a higher cost. These are usually the best options for each item.
The "Other good values" chart just shows the lowest cost options that are not on the Local Minima chart. These can be useful if you don't like the Local Minima options, such as if the low XP Cost from the minima table has an Item Cost that is too high.
Past the summary section are the sections on each item. These have the same four tables as in the summary, but they only include options for one specific item. The item sections also include graphs of the two cost values for each level from 1 to 50.