>What is the utility of clause WITH (NOLOCK) in SELECT FROM ?

If you have connections with pending transactions that are locking rows in a table and you don't have this hints, no rows will be returned before the rows get unlocked. If you specify this hint, you will get the last known state of the rows (often known as dirty-read).

I have used the term "rows" but most often, a complete 8K page is locked even if a single row as to be locked.