BOLT & rts

Hi, is there any detail description of the meaning of rts?

BOLT> help rts
  SUMMARY
     list all, or select an rts
  USAGE
     rts [-set N] where N is the number shown when listing rts sets
  OPTIONS
     -set=* ........... Program and save to flash an rts set
     -clear ........... Uprogram and unset flash saved rts set (will
                        then use board defaults)
*** command status = 0

BOLT> rts
rts 00 [20150422212833_boot_box0]
rts 01 [20141112013607_1stb1t_box1]
rts 02 [20141112013452_1u2t_box2]
rts 03 [20141112213819_4ku0t_box3]              *default
rts 04 [20141013221002_4563_2t_box4]
rts 05 [20150202223821_4ku0t_box5]      *used
BOX MODE: 5
*** command status = 0