a player becomes unrestricted when he has served a designated amount of years to one club, he can pretty much go where he wants.
a restricted player has also played a certain amount of years but the club he is playing for has the right to match a rivals offer in monotery terms. if that happens they stay put.
jake lever was out of contract after about three years and wanted to come home, this is when all the trade toing and froing takes place and that's why we gave up what we did to get him.
the players fought for this in the last agreement a few years ago.
I may be wrong but restricted is after six seasons, unrestricted after eight. something like that.