First time DM here and i have a rogue in my party, and as i was reading the description for Sneak Attack i noticed it doesn't say that one need to be hidden or out of sight to be able to apply this extra damage, one just need to have advantage on the roll or an enemy of the target 5ft of him? 

So am i interpreting this right by saying there is no need for the rogue to be hidden or out sight of the enemy to apply sneak attack bonus damage?

Thanks in advance for your help.

Yes, you are interpreting it correctly.

Thank you very much, i was kinda confused with the wording of the description and the name of the attack itself

You can consider the "sneak" part to be an attack in an unexpected way.  With the enemy within 5 ft, the creature is trying to watch both enemies and the rogue uses the split attention to sneak a particularly nasty blow in.  With advantage, the rogue has something that has otherwise given him the upper hand and uses that to deal a particularly nasty blow. 

Do keep in mind that some of the subclasses have additional ways to trigger sneak attack, but you'll only need to worry about them starting at level.

Being hidden is a means of getting advantage, but that's the only direct relevance.