What is meant by -2*LogLikelihood in Gaussian Process model report?

[#1]

I am applying Gaussian process model to my data set. But wondering what are the mathematical meanings of this -2LL (-2*LogLikelihood) term? Is there any formula for this (literature)?
I have searched in literature, I only found negative logLikelihood instead of -2*LL. Why JMP take twice of negative?

 

[#2 · Accepted solution]

This page explains what and why the -LogLikelihood (and -2LogLikelihood) is used. 

[#3]

Thanks