What does "bleed" mean in the business card design tool tutorial?

Bleed is the extra 0.0625 inches of design that extends past the trim line on each side. It exists because cutting machines shift slightly, and the bleed gives that movement somewhere to go so no white edges appear.

• Bleed amount here: 0.0625 inches per side.
• Extend background colors and images fully into the bleed.
• Keep important text inside the safe zone, away from the trim.
• Skipping bleed risks thin white lines along the finished edges.