Consider situation when one user doing his transaction, then meantime other users from my understanding are not able to delete/update specific table - but what about read, are they able to read, and if so what will be data they would see? And what if they going to delete/update some records are going to get timeout due to transaction is ongoing? Any easy to understand example appreciated.
I think what you're looking for is WITH (NOLOCK).
SELECT * FROM YourTable WITH (NOLOCK)
It will allow you to read uncommited rows of data.
For more info refer here.
Regarding the simultaneous changes in the table: Simultaneous insert/updates etc. are theoretically impossible since SQL Server serializes it inside (like a log) having nanoseconds as an interval, thus making it impossible to create a simultaneos modify at the same time.