What is the encoding of APRS?

Could you please elaborate on the encoding of APRS? I'm curious to understand the specific methodology or algorithm used to encode the data within the APRS system. Is it a proprietary encoding scheme or does it adhere to any widely recognized standards? Additionally, how does the encoding process ensure the security and integrity of the information being transmitted through the APRS network? Understanding the encoding of APRS is crucial for assessing its overall reliability and efficiency in transmitting data.