Hi Greg and welcome to TFL.
You are right that the SPL on the side of your barrel is for 'special'. You will never see a box that just says ".38" because there are several different types of ammunition in that caliber. (ie, .38 short colt, .38 long colt, .38 S&W, .38 WCF and etc.)
Also if your gun is marked with the +P on the barrel it will fire .38 spl +P ammo as well, which is loaded a little more powerful than the standard .38 spl. Many guns that aren't marked +P will fire them also, although some shouldn't be used with them. Just in case that question ever comes up.