SQL & PL/SQL

hi
i really appreciate the answer i got fro u guys about the table , iam clear now i have a question why do i need to have a logical structure over a physical structure called table, ultimately my data is in db blocks , so can we say that when i query a row in a emp table
dbms checks---- which tablespace the table belongs to
----which segment in that tablespace the table data is sitting and then it goes to extent and finally retrieves from the hard disk
so can we say the retrieval becomes easier
am i correct , pls give a simple explanation as to what is the benefit