Sigh that my first reply LOL
A ranked queue is a list of player all given a number based on skill.
The players compete to increase there rank.
This gives players something to obsess over thus increasing the player base
and making it much easier for people to got into game faster.
In a latter system higher skill players will be able to avoid games with low skill players ,
and get way more game with high skilled people faster easier.
i hope this helps ^.^