Fanboys has a few meanings, but one very particular in English grammar. In English grammar FANBOYS is a mnemonic device to help learners remember the main conjunctions:
F - for
A - and
N - nor
B - but
O - or
Y - yet
S - so
This guide to conjunctions and their use will help you learn these FANBOYS and their proper usage.
Here in the United States, fanboys also refers to the people who love Apple computing products (and other systems, but generally it refers to lovers of Apple). That's not really important to know, but it's an interesting idiomatic expression.
Notice how I used one of the FANBOYS 'but' in the last sentence!