Mobile service: What is peer-to-peer SMS ...? Also, what is the "specific" difference between a call reminder and a caller ID ...?

Peer-to-peer refers to SMS from mobile phone to mobile phone. Call reminder means that when your mobile phone is turned off or there is no signal, or it is set to not answer the phone, if someone calls you, when you restart your mobile phone, enter the service area or reset to answer, there will be a short message to remind you who called you during this time (prompting you for the calling number). Caller ID is a service that can display the caller's calling number when your mobile phone is in normal use and turned on.