TIG welding, also known as Gas Tungsten Arc Welding is defined by the American Welding society is an arc welding process that uses a non-consumable tungsten electrode to produce a weld. 

The weld area and electrode are protected from oxidation or other atmospheric contamination by an inert shielding gas normally argon or helium. Commonly a filler metal is used, though some welds, known as autogenous welds, or fusion welds do not require it. GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminum, magnesium, and copper alloys. 

Advantages

• Allows for the welding of more metals and alloys than any other welding process
• Creates precise, high quality, clean welds
• Little to no clean up due to the lack of spatter and sparks produced while welding
• Little to no smoke or fumes created unless the base metal contains contaminants
• One shielding gas (argon) for all applications
• Can be welded in all positions

Disadvantages

• Improper gas coverage can lead to contamination issues
• Overheating the weld area can cause significant problems such as cratering and can impact the mechanical properties of the weld area
• Oxidation can form around the weld area more easily known as “sugaring”
• A two-handed technique that requires a more skilled welder
• Less forgiving than other welding processes, using incorrect technique is much less forgiving and will create inferior welds