Number of holes is very easy to understand these are the number of holes that are there in an alloy wheels. These holes are very particular for the alloy wheel to be compatible with a car. These number of holes are to be the same as the number of bolts that are there on the wheels axle. Each car manufacturer has their own methodology for defining the number of bolts on the axles. Usually the smaller cars would come with 4 bolts and bigger cars would come with 5 bolts. Hence mostly 4 holes wheels are compatible with smaller cars and 5 holes wheels are for bigger cars. Number of holes is accompanied by the diagonal distance between these holes which is called PCD for defining any alloy wheel for a car. We will be talking about PCD in our other article. So usally wheels are embarked as 4*100 or 4*108. Here 4 is the number of holes and 100 or 108 is the PCD.
You might have noticed there are wheels which have 8 or 10 holes as well. So for which cars are these holes suitable for? The answer is multiple. Manufacturers nowadays have come with wheels with multiple holes and PCD options. For example if an Alloy Wheel reads 10*100+108. This means that the alloy wheel is actually having 2 sets of compatibility 5*100 and 5*108. because of this option now a wheel is compatible with more cars. So incase in the furture you want to change your car but keep the same wheels the options are wider for you. As well the resale values of these wheels goes high as they are compatible with more cars.