Once you get a character to level 250, you can opt for a Rebirth. You can only rebirth 3 times.

This will happen to your character:

• Lose your Experience (back to Level 8)
• Keep your skills, items and house
• Get your Stamina back to 100%

This gives you the following advantages:

• Access to Rebirth Spawns (previously these where VIP spawns, accessible from the Thais Depot teleport)
• 50% magic find
• 25% chance to get eggs
• 2 weeks of VIP
• 100 rebirth points

You can buy exclusive items:

• Skull Remover (20 Rebirth Points)
• Magical Box (15 Rebirth Points)
• Golden Falcon (60 Rebirth Points)

Here's the thread where rebirthing was discussed

You will go from level 250 to level 8 so your capacity will be decreased and your level-dependant equipment will not be available.

Your Stamina will get back to 42:00 so don't waste a Scroll of Stamina at level 249 if you don't have to.