screen burn?

[saprano]

i have a 40"samsung lcd and when im playing a game, or wacthing a movie, it seems like when i chang the screen i can still see the last image that was on the sreen. is this sreen burn? it does not stay there as when i chang it again is goes away, but does anybody know why this happens, or if its sreen burn thanks.(oh and buy the way,i think i used around 150 hours on my tv already if that helps)