Using VarCorr to calculate correlation matrix

I’d like to create a correlation matrix for regressors in a hierarchical model, and I’ve come across the function VarCorr.brmsfit here: https://rdrr.io/cran/brms/man/VarCorr.brmsfit.html. However, I’m unclear on what the output is exactly - does this function calculate correlations between regressor input or regression weights? Thanks, I appreciate any advice.

The keyword in the link is estimated. The correlations are calculated between parameters not between the input data.

Executing the example in the link,

VarCorr(fit) provides.

$visit$cov
, , Intercept

            Estimate Est.Error         Q2.5     Q97.5
Intercept  3.6711353  9.455393   0.00225775 25.957742
Trt1      -0.7187569  5.660284 -13.24285644  4.487274

The Intercept line shows the variance and Trt1 line the covariance between Intercept and Trt1.

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