What is the best boy do?

[Harry Edwards]

I was reading an online article about "gaffer' and I stumbled upon the term "best boy". I am a bit confused because I did not find any further details, this term was just mentioned in the article.
So what exactly does the best boy do on the movie set? What is their purpose?

 

[Olivia Perez]

From my knowledge, he's the electrician that works with the gaffer.