• ra, dec: each individual file contains the (ra, dec) of all the bdbs sources in the tile
• ra_vvv, dec_vvv: are the coordinates of the closest VVV match
• sep2d_arcsec: is the angular separation in arcseconds
• ejk: E(J-K) as in Simion et al. 2017; Ak = 0.482 x ejk and Aj = 1.351 x ejk
• Jmag, Ksmag: VVV magnitudes not corrected for extinction
• err_j, err_k: photometric errors for the Jmag and Ksmag

Note: to find the matches, I recommend sep2d_arcsec < 1''. \

In the crowded fields notice that sep2d_arcsec can be of the order of a degree or several degrees