index-rebuilding

I have a table in which i have a index for a column,now i delete all the rows
from that table ,then i insert new rows into the same table.Now what will happen to the index of that table,should i rebuild the index in that table.Please suggest me.

It is strongly recommended to rebuild the index for better performance.

Thank you for your suggestions,but can u tell me what will happen to that index which was in the table.

The index will remain there but with new mapping to the addess of data in the column.