It's a relic of SAT verbal analogies section which was removed in 2005. The syntax "A:B::C:D" represents the statement "A is to B as C is to D".
So on the test you'd get questions such as
python:snake :: ___ : ___
a) lua:satellite
b) swift:bird
c) java:coffee
d) pearl:gem
and you might select A because python is an interpreted scripting language and a type of snake in the same way lua is a scripting language and a type of natural satellite but you'd be wrong because the correct answer is B because the topic was actually about comparing animals.
So on the test you'd get questions such as
and you might select A because python is an interpreted scripting language and a type of snake in the same way lua is a scripting language and a type of natural satellite but you'd be wrong because the correct answer is B because the topic was actually about comparing animals.