The average person likes to be unique and a lot of insecurity is driven by the fear of being replaced, science doesn't do anything to reassure us when by positing that the average person has 6 or 7 doppelgangers out there. While we have to accept the fact that there are people who will look like us and/or sound like us, software engineers don't think it's a great idea to pass on that narrative to machines as such we created something that can somewhat give everyone a unique identity.
A RELATABLE EXPLANATION
We have a term know as " Globally Unique Identifier" (GUID for those who use Microsoft technologies, yes, special people like me 😎) or "Universally unique identifier" (UUID for everyone else) which is used to generate 128-bit integer values. GUID/UUID is touted to be so unique that you won't find a reoccurrence of the same values ever again. While you might be doubtful, the claim is actually reasonable seeing as 128-bit integers have 2^122 or 5,316,911,983,139,663,491,615,228,241,121,400,000 possible combinations 😲.
ORDINARILY, WE GIVE INCREMENTAL ID NUMBERS
It's ok if you can't put those numbers in words, I can't either 😂. The field of software engineering is becoming quite reliant on GUID/UUID, it's popularly used in assigning a primary key or ID to individuals who register their details on a platform or software solution. When we register on platforms, our data gets stored in the database and such data is called whenever we try to log into that platform, the default way databases allocate space is by giving people a row with a number identifying that row (as we see on Microsoft Excel).
GUID IS IMPORTANT IN REDUCING THE POSSIBILITY OF SWAPPED IDENTITY
As a result of the fact that our names aren't exactly unique (if by chance yours is, it won't be unique in a decade 😏), we need to be able to differentiate between two people with the same name and other details so as to match each person with their appropriate resource. Imagine for a second how you would feel if you log in to Hashnode and your profile look different, so are your details and all because the platform mistook you for someone else who bears your name. While it's excusable for humans to make such mistakes, machines have to be more precise. Something so small can have huge consequences if the database of your bank can't tell the difference between you and someone with a similar name and ends up swapping your account balances 😱.
FINALLY
By now you get why everyone has to be unique online. GUID/UUID aren't just for ensuring everyone's ID is unique, and improving caching, but also as a security measure as there are ways people can hack one's online identity by randomly trying ID numbers and trying to bypass authentication and role assignment (something that is now termed "broken access control"). It's a lot harder to guess a GUID/UUID because it's lengthier and more stressful. GUID is more secure and gives developers more confidence in the application's ability to tell things and people apart. We still use the standard (incremental) ID process for less important things.