LVextend

[Raj Har]

Hello all,
                i have one confusion please help me.

1.suppose we creates 500M PV
2.500M VG1
3.200M lV1
4.format with mke2fs -j /dev/vg1/lv1
5.mount /dev/vg1/lv1 /new
6.i want lvextend
7.when we extend lv from vg. after extend we need not to format this
partation we run resize2fs command for using this partition.

why we not need to fromat this partition?
when we create first time lv we format it bt not in extend case why?

thanks