Boolean usually refers to logic. (Mr Boole was an eminent mathematician)
The most common statement in logic are AND, OR, NOT. A boolean search combines key words together using logic statements to link them together. Like this
cat AND dog
In this case, the search will find items that have both the word 'cat' and the word 'dog'.
cat OR dog.
In this case, the search looks for either 'cat' or 'dog' being present.
Another useful boolean term is NOT as this is very handy to exclude search results. For example, say you were looking for articles on Jaguar cars, so you don't want to see articles about the wild animal 'Jaguar'. A good boolean search term would be
Jaguar NOT animal
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Boolean Search