The PC(Player Character) has the ability to put "ranks" into specific skills. These skills are mere things that anybody can do, such as search, spot, use rope, climb, swim, ride, etc. They are not skills such as those found in RMXP. These skills are rarely called upon at critical moments, but are rather subtle events that affect gameplay. Here is an example: You dropped a few coins in a dim-lighted bar full of people, in an attempt to find them all, you must use a search check. Usually in DnD, the DM (dungeon master) will roll the die and add up the points to determine if you find all of them, or which ones you find. A random variable(such as a 20 sided die[d20]) is rolled, then added to the PC's intelligence modifier(The governing attribute of the search check), and then added again to how many ranks the PC has in search.
d20+int mod+ranks = final score
This is then compared to the DC(Dice Check) score that is required to find some coins. If it exceeds, then the player finds all the coins. If it falls short, the PC may find a few coins, or none if he rolled low enough.
Normally, the DM rolls a d20 to find a random number between 1 and 20, but you may change this in order to make it work right with your project.