The ABB XT4XU3250EJJ000XXX is a 3-pole breaking part from the XT4X molded-case switch-disconnector family, rated for the 250 A frame size with fixed front terminals and UL/CSA certification. It's the interrupting section of a UL 489 / CSA C22.2 No. 5 switch-disconnector — the part that actually opens and closes the circuit under load. In a panel, this breaking part mounts into the XT4X base and operating mechanism assembly; you'd spec it when building a UL-listed disconnect switch for motor branch circuits or distribution feeders.
What the UL/CSA mark means for your panel
If your panel ships to a US or Canadian job site, that mark is what the local inspector looks for. The fixed front terminals accept standard bus bar or cable connections; no special adapter needed for a 250 A feeder.