Underscore Necessary in Table Prefixes?

Installing opencart, is an underscore "_" necessary in table prefixes?

What will happen if I use "prefixname" only instead of "prefixname_" ?

Its not compulsory to use underscore in prefix

example :
table prefix = mystore
table names :- mystoreorders , mystoreproducts etc...

table prefix = mystore_
table names :- mystore_orders , mystore_products etc...

conclusion - easier to read table names

So its only for readability of the developer and nothing to do with database function.... is that correct?

Yes, the underscore is not required. It's just a database convention to prefix the tables with something related to the software, followed by an underscore.