What is a anti-image correlation matrix?

Hello, I am currently doing an homework on Factor Analysis and PCA in SPSS and I have to present the Anti-image matrix and explain what it is. However, after having searched on google, all I found was this : The anti-image of the correlation matrix is the negative of the partial correlations, partialling out all other variables

What exactly is the "negative of the partial correlations". Is it the negative correlation, or another indicator (like 1 minus the partial correlation value)? I really need to understand this anti-image matrix and Internet isn't helping...

Thank you!