What does 'Best thing since sliced bread' mean?

If something is the best thing since sliced bread, it is excellent. ('The greatest thing since sliced bread' is also used.)

• Category: Food

Idioms similar to 'Best thing since sliced bread'

• There's no such thing as a free lunch
• White-bread
• Bread and butter
• Bread and circuses
• Half a loaf is better than no bread
• Quarrel with bread and butter
• Know which side one's bread is buttered on