a plug or slot weld is what type of weld, just prepared differently?

AWS D1-Series References to WPS for Plug and plug weld vs slot weld Single-U butt weld 8 Single-U butt weld 9 Backing run; back or backing weld 10 Fillet weld 11 Plug weld; plug or slot weld plug and slot weld Slot weld is also shown in the figure above It is quite similar to the plug weld, except that the hole is not circular, it is an elongated hole

plug slot weld This document defines plug and slot welds and discusses how they are represented in welding symbols Plug welds use a round hole while slot