Each case represents a particular voting-country in a particular year.  
There are data on: 
the year of the competition [voting_year]
the semifinal in which the voting-country appeared [semifinal_appearance]
and the number of votes they gave to a particular contestant-country that year.

Each of these votes is a separate variable. The name of the variable denotes the contestant-country, the year of the competition, and which semifinal they appeared in.
Thus, [israel08_1] shows the number of votes given to Israel's act in 2008.  The number at the end of the variable name indicates that they appeared in the first semifinal that year.

There are two further variables derived from these:
the total number of votes each case gave to contestants who had previously appeared in the first semifinal [SF1_total]
the total number of votes each case gave to contestants who had previously appeared in the second semifinal [SF2_total].