There is a specific pattern for each lock and key made in the world. A specific key can only open a specific lock which has the same pattern in which the key can fit.
This thread here suggests that there are millions of locks with the same key.
Yes, there are millions of locks with the same key. Think of it this way... Master lock has 8 depths and four pins for most of their locks.
8x8x8x8 = 4,096 possible key permutations, including keys that exceed MACS (Maximum Adjacent Cut Specifications). The actual number is lower than that. Yet Master Lock makes many thousands (hundreds of thousands?) of locks a year.
Kwikset has six depths and five pins for their normal home deadbolt lock.
6x6x6x6x6=7,776 permutations, again including those that exceed MACS. They must sell a million of those locks a year.
Many other commenters in the same thread make consistent claims.
Is it possible that somewhere in the world, two locks can randomly be of the same pattern - i.e. One key can open two different random locks?