A2P (application-to-person) SMS is any text message sent by software to a person: verification codes, alerts, receipts, reminders and marketing campaigns, as opposed to messages typed by one person to another.
A2P stands for application-to-person. It covers every SMS sent by a system rather than a human: one-time passcodes, delivery notifications, appointment reminders, fraud alerts and promotional campaigns. Carriers treat A2P traffic differently from person-to-person traffic: it is priced per message on wholesale routes, it may require a registered sender in some countries, and it is filtered for spam more aggressively.
The distinction matters because carriers detect A2P traffic sent through person-to-person channels, for example SIM farms, and block it. Legitimate A2P traffic goes through a gateway connected to carriers on A2P terms.
At SMSMeteor: all traffic is A2P and carried on routes chosen per destination for delivery rate; the sender rule for each of the 228 destinations is listed on its coverage page.