Why so many types of sim in the store

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@l124377322 wrote:
SIM for 4G LTE Android™, SIM for 4G LTE Windows® Phone, SIM for Apple® iPhone® 4s, etc.
As long as the size and frequency bands are compatible, I can use my sim card among multiple devices, am I right?
I think SIM for 4G LTE Android is the same thing as SIM for 4G LTE Windows® Phone, and it should be compatible with iPhone 4s, is that correct?
I am so confused why there are so many types of sim while they work on the same network.

I want to bring my own phone to a new plan but when it ask me to choose my sim I don't know what to do. I am using an iPhone 4s now but I am going to upgrade to an Android very soon. They both use a micro Sim card so I think I can order a SIM for 4G LTE Android™ and when I upgrade I can just take it out of my iPhone and put it in my new device, but I am not sure if this will work?
I have a lot of questions. Can someone give me a clear answer?
Thanks.

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The short answer: you're right, all that matters is the SIM size.

The long answer: AT&T uses minor differences in the account setup to enable some more advanced features and while moving the SIM card from phone to phone will keep voice, SMS & internet working those other ones may not work properly. For example, tethering may not work in the other device if you move an Android SIM into an iPhone and vice versa. FaceTime over cellular will likely not work with an ANdroid SIM and so on.  What labeling those SIMs as "for Android", "for iPhone", etc. does is make sure that those little details about the associated account are set up correctly on the AT&T end. Most of the time if you discover features that are not set up correctly a call to AT&T is all it takes to straighten it out, you don't have to replace the SIM.