What does “+6 to hit, Hit: 13 (2d8 + 4)” mean in a creature’s stat block?

My friends and I are very new to D&D, played like 3 times. In a monster’s stats next to weapon damage it says stuff like “+11 to hit” and “Hit: 5 (1d8+1)”. For the premade characters it just says things like “+4, 2d6 + 2 slashing”, though. Why are there two “hit” numbers for monsters? Which do I use for the d20 roll to hit against a target’s AC?

I mean for example like in the Ogre entry in the “Starter Set: Excerpt 7” article on monsters.