The Intel Centrino concept is a package designed for people who rather have a laptop with a good amount of battery power than a power-notebook with 1 GB of ram, 3 GHz proc etc etc. 3 things are different from normal laptops:
The Intel Pentium Centrino CPU's are clocked at a lower rate to preserve energy. To compensate that, they have double the L2 cache a normal Pentium4M has, 1 MB instead of 512 KB;
The Intel 855m mainboard can handle the available battery power more efficiently
An Intel Wireless card has been added to the laptop (infact it's mounted on the mainboard).
So if you need a good laptop for office use and/or internet and you need the extra hours of laptop fun, go for a Centrino.