# sms

- [What is a STOP keyword, and what must happen when someone sends it?](/explained/sms/what-is-a-stop-keyword)
- [What is A2P vs P2P messaging?](/explained/sms/what-is-a2p-vs-p2p-messaging)
- [What is an alphanumeric sender ID?](/explained/sms/what-is-an-alphanumeric-sender-id)
- [What is an SMS API, and how does it differ from an SMS gateway?](/explained/sms/what-is-an-sms-api-vs-an-sms-gateway)
- [What is an SMS segment, and why did one message cost three?](/explained/sms/what-is-an-sms-segment)
- [What is an SMS template, and do templates need approval?](/explained/sms/what-is-an-sms-template)
- [What is an SMSC?](/explained/sms/what-is-an-smsc)
- [What is bulk SMS?](/explained/sms/what-is-bulk-sms)
- [What is GSM-7 vs UCS-2 encoding?](/explained/sms/what-is-gsm-7-vs-ucs-2-encoding)