AF: Alternate Frequencies. This allows a receiver to re-tune to a different frequency providing the same station when the first signal becomes too weak (e.g. when moving out of range). This is often utilised in car stereo systems.
EON: Enhanced Other Networks. Allows the receiver to monitor other stations for traffic broadcasts.
PTY: Program Type. This coding of up to 31 pre-defined programme types – e.g. (in Europe): PTY1 News,
PTY6 Drama, PTY11 Rock music – allows users to find similar programming by genre. PTY31 seems to be reserved for emergency announcements in the event of natural disasters or other major calamities. This allows you to search for ROCK stations, news etc.
TA, TP: Travel Announcements, Traffic Program. The receiver can often be set to pay special attention to this flag and e.g stop the tape or retune to receive a Traffic bulletin. The TP flag is used to allow the user to find only those stations that regularly broadcast traffic bulletins whereas the TA flag is used to stop the tape or raise the volume during a traffic bulletin.
TMC: Traffic Message Channel. Demands a RDS-TMC decoder.
AST switches to FM-AST or MW-AST band, searches for the 6 strongest transmitters and stores them
in the AST programme preset memory. In FM, duplication of PI codes will be avoided.
Hope this helps :)