From VDR Wiki
The EPG (Electronic Program Guide) is the digital variant of a printed TV magazine. With the Help of the EPG one can see the schedule of nearly all broadcasters.
This overview contains the title, date and time of a telecast. Additionally to this information, one can get a small summary of a telecast. Together with VDR, this information can be used to program a timer.
The side band 300-399 of the videotext is already an ancestor of EPG. A more advanced variant for analog TV is the NextView system which many manufacturers use.
With digital TV, the EPG data is transmitted according to DVB SI EIT standard. Digital receiver normally dispose of a build-in EPG decoder and can display this data on TV. External EPG, e.g. after the MHP standard, have additional features, like images or more detailed information.