Arc welding electrodes are identified using the A.W.S, (American Welding Society) numbering system and are made in sizes from 1/16 to 5/16 . An example would be a welding rod identified as an 1/8" E6011 electrode.
The electrode is 1/8" in diameter
The "E" stands for arc welding electrode.
Next will be either a 4 or 5 digit number stamped on the electrode. The first two numbers of a 4 digit number and the first 3 digits of a 5 digit number indicate the minimum tensile strength (in thousands of pounds per square inch) of the weld that the rod will produce, stress relieved. Examples would be as follows:
E60xx would have a tensile strength of 60,000 psi E110XX would be 110,000 psi
The next to last digit indicates the position the electrode can be used in.
EXX1X is for use in all positions
EXX2X is for use in flat and horizontal positions
EXX3X is for flat welding
The last two digits together, indicate the type of coating on the electrode and the welding current the electrode can be used with. Such as DC straight, (DC -) DC reverse (DC+) or A.C.
I won't describe the type of coatings of the various electrodes, but will give examples of the type current each will work with.