There are two main formats of videos available
today - VHS-NTSC and VHS-PAL. NTSC (National Television
Standards Committee) is the format that is used mainly in North
America, Japan and Taiwan.
Make sure you choose the right format when you buy videos!
NTSC video is formatted for 60 fields (30 frames) per second. PAL standard is 50 fields (25 frames) per second. American power is 120volt at 60hz, Europe is 240volt at 50hz. The lights in a house in the US flash 60 times per second, so they need to be in sync with the TV so you dont see flicker between the two.
DVDs currently use one software format for "Region 1" countries and another format for "Region 2". However, as part of a growing industry trend, many DVDs (such as the Alfred DVD of "Martin Simpson Teaches Alternate Tunings" and the SGGW "Martin Simpson in Concert" DVD that we sell here on the Watershed Arts website) are "Region Free", meaning that they work work anywhere on the planet, in any DVD player.
Below is a more complete list of countries sorted by video format.