The 50Hz pal and 60Hz NTSC carries over to HD in frame and refresh rates.
60Hz systems USA/Canada among others get:
24p = progressive 24 frames per second
Mostly used for film to video transfers (DVD, BD) as most 35mm films are 24FPS. Starting to be used in special MPEG-4 cable and satellites transmissions.
30p = progressive, 30 frames per second
Sometimes used in broadcast, satellite and cable.
60i = 60 interlaced fields, 30 frames per second
The most common for broadcasts, satellite and cable.
60p = progressive, 60 frames per second
Starting to be used for special programming via cable and satellite using MPEG-4 delivery.
30 is actually 29.97
60 is actually 59.94.
50Hz systems, UK, most parts of Europe.
25P = progressive 25 frames per second
50i = 50 interlaced fields, 25 frames per second
50p = progressive, 50 frames per second