These bearings uses long, thin cylindrical rollers resembling needles, they are used to reduce the friction of a rotating surface. Due to greater surface area they can support greater load.
A needle Roller Bearing is a bearing which was small cylindrical roller.
The difference of a needle roller bearing and roller bearing is the ratio of Dia. and length of roller bearing is between the interval of 0.4 to 0.1, that roller bearing is called needle bearing.