When a Apple employee sells you an "unlocked" iPhone, what does that mean exactly?

I have included the Apple LTE website link below.

iPhone - View countries with supported LTE networks - Apple

There are 5 types of iPhones.

Sprint, Verizon, & Sim-Free iPhones are the truly internationally unlocked iPhones. They all work the same basically.
Which basically means you can use all carriers, CDMA & GSM.

T-Mobile & AT&T iPhones are GSM Only. These you cannot use with Sprint/Verizon although the former you can use with T-mobile/At&t.
This will still work for many US/international carriers, with the exception of places like China, Hong Kong, Puerto Rico.

Only the Apple Store sells Sim-Free iPhones(Full Price will say unlocked on the receipt), but generally an iPhone activated through a plan will be an iPhone corresponding with that plan.
Ex. If you go to Sprint you will get a Sprint iPhone. T-mobile has T-mobile iPhones.

Unlocked means the phone is not tied(locked) to one number.

Financing generally ties your phone number to that android/iPhone, which will lock it until you complete the payments.
Only Apples Iphone Upgrade Program lets you have the phone not be tied to a number.

So if you're looking to buy an Internationally unlocked iPhone to use with any carrier, you must purchase a Sprint, Verizon, or Sim-Free iPhone. Reminder that this only applies if you want to use carriers on the Sprint, Verizon, or the list of CDMA carriers I have included in the link below. This rarely is applicable to many unless you are taking the phone to China, Sprint, or Verizon & you currently have a T-mobile or At&t One. Due to the fact the GSM iPhone works with almost 90% of carriers anyways.

I have included the Apple LTE website link below.

iPhone - View countries with supported LTE networks - Apple

Summing it up, if you are never going to use a Chinese, Hong Kong, Puerto Rico, Sprint, or Verizon Carrier, or plan to sell to someone with those carriers, then any iPhone is fine. If you pay it off, it will be unlocked.
If you need internationally unlocked Purchase a Sprint/Verizon/Sim-Free Iphone.

Otherwise T-mobile/At&t Iphones will work with most international carriers anyways.

If you buy an unlocked phone from an Apple store it is truly unlocked, and it will work anywhere in the world. But you must buy it from Apple directly. Phones purchased from other dealers, such as Best Buy, will lock to the first carrier they are used with.

Hi trillmix

I suspect what 'apple employees' mean by an 'unlocked' iPhone is that it remains unlocked only until you put a 'network sim card' in it.

Whether this is different in YOUR country, I have no idea (I live in the UK)

I would take the Apple Employee statement to mean that you can probably use ANY networks sim card you want to, but it then gets 'locked' to that network AFTER you either insert 'their' (not apples) sim card, or actually start to use it in that previously 'unlocked' and admittedly brand new smartphone (or iPhone in your case).

Previous 'officially unlocked' & relatively cheap 'dumb phones' (priced compared to smartphones) I have had have remained unlocked after using at least two, if not three, different UK networks PAYG sim cards.

The last one I bought about 8 years ago still worked after at least 6-7 years and was still unlocked.

Previous contract smartphones (normally locked when you get them in the UK) & ALL made by HTC, that have been 'unofficially unlocked' well AFTER end of warranty/contract tarriff, have permanently failed VERY soon afterwards.

My lesson is this:

Get an OFFICIALLY unlocked phone - if you need it to be PERMANENTLY unlocked - no matter what sim card you use in it.

Get that confirmed in writing - especially if the phone is a Smartphone or iPhone.

NEVER get a 'cheap mobile phone accessory trader' and so called 'expert' to 'unlock' your contract Smartphone or iPhone - that will still be OFFICIALLY LOCKED - even well AFTER that contract has expired.

This has caused all three of my previously locked 'contract' SMARTphones to permanently fail very soon afterwards.

Perhaps the 'experts' broke them, perhaps OFFICIALLY LOCKED HTC Smartphones will always die after 'unofficial unlocking'.

Perhaps most or ALL LOCKED Smartphones CAN be unlocked OFFICIALLY (but only by the manufacturer?), without breaking them, perhaps they CAN'T.

My iPhones have never failed & never been unlocked, because I have stayed on the same network since before I had an iPhone.

Hope some of this helps

Bob