What is the Ligand-RMSD meaning and calculation for peptide protein interaction?

Question

[soobiney]

hello,

I would like to know estimate the peptide binding site on the receptor. so i used the CABS-DOCK website, and I got the "Cluster name", "Cluster density," "Average RMSD (Å)", "Maximum RMSD within the Cluster (Å)", "Number of cluster elements" .

In several papers, they says "Ligand-RMSD value", so i wonder the "Lingad-RMSD" meaing and how to calculate Ligand-RMSD value?.

thank you in advance.