This article is from the Europe FAQ, by Yves Bellefeuille firstname.lastname@example.org with help from Martin Rich M.G.Rich@city.ac.uk.
These acronyms refer to the systems used by television broadcasts and
videocassette players (VCR).
The USA, Canada and Japan use the NTSC system. France, Greece and most
"Eastern European" countries use SECAM. The rest of Europe uses PAL.
A television set will only work with a specific system. For example, a
television bought in a country that uses NTSC won't work in a country
where the broadcasts use the PAL system. Keep this in mind if you're
planning to bring a portable television set with you; TVs bought in
North America or Japan won't work in Europe.
Similarly, a videotape will only work in a videocassette player (VCR)
that uses the same system; thus, if you're from the USA and want to buy
a videotape in Europe to watch it later at home, make sure it's in NTSC
formal. It's possible to have a videotape converted from one format to
another, but it's rather expensive and the results are often poor.
For more information, see http://www.faqs.org/faqs/de-film/formate/.
This document is in German, but the list of formats used in various
countries in section 1.3 should be easy enough to understand.