what is the difference between activating an iphone and activating a sim card?

[stradi]

Edit

[HakoneRider]

So far the only phone requiring activation that I have used is the iPhone. Maybe other smartphones need "activation" but I don't know any others. As far as "activation" goes, the iPhone only needs it because Apple wants to make sure it is being used on an officially supported network.
SIM card activation is done by your cellphone operator and is required for you sim to actually allow your phone to communicate.