PCTFREE for indexes

hi,
Can someone help me out why do we use a pctfree for indexes,
by books i find that indexes are not updated( since it is a logical delete and insert).Please do reply to this query of mine it would be really helpful.
have a good day!
regards,
S.Ramya.

PCTFREE meanssomething different on an index -- it refers to the minimum amount of freespace to be left for future entries when an index is initially created or rebuilt.