Update index.rst

doc/DESI_ROOT/survey/catalogs/RELEASE/LSS/SPECPROD/LSScats/VERSIONpip/index.rst

@@ -2,7 +2,7 @@
 VERSIONpip
 ==========
 
-VERSIONpip contains same catalogs as VERSION, but with PIP weights. Healpix maps are the same and are found in the same VERSION directory
+VERSIONpip contains same catalogs as VERSION, completeness weights that are built from the record of alternative fiber assignment histories. These assignment histories also allow pairwise-inverse-probability (PIP) weights to be calculated for 2-point clustering measurements. Healpix maps are the same and are found in the same VERSION directory
 
 .. _Ross et al. (2024): https://arxiv.org/abs/2405.16593