Every licensed Radio Amateur is given a call sign that is used to identify them and their location of license. Each country that has Amateur Radio status is allocated a range of call signs by the International Telecormunications Union (ITU).
Call signs consist of a prefix and a suffix. The prefix is usually composed of one or two letters and a number such as VE4 in Canada for the province of Manitoba or K9 in the U.S. for the states Illinois, Indiana, and Wisconsin. Some countries have prefixes that are composed of a number and a letter such as 4X for Israel or 9K for Kuwait. If this sounds confusing tables of call sign allocations will be given later in Materials section to make things clear.
While the prefix is unique and identities a country the suffix is unique for the individual. In Canada a call sign such as VE3ABC hasVE3 (Ontario) as the prefix and ABC as the suffix. In the U.S. the call sign K6XYZ has a prefix of K6 (California) and suffix of XYZ U.S. hams may also have a two letter prefix thus AB2Z is a valid call. Suffixes may also be less than three letters so you have call signs such as VE7AB in British Columbia and KH6Y in Hawaii. Some countries, e.g. Russia may have suffixes showing more exact location of the ham station, thus serving as addition to the prefix. So, RA6LO, for example, gives the following information: RA - country Russia; 6 - Nothern Caucasus; L - Rostov region; O - individual part of suffix. Two letter after a call sign in Russia, mean the high category of the operator, lower categories have three characters in suffix.