Not all tarps are the same. Yes, they vary in material, thickness, size, grommet strength and type, and uses. It is useful you know some details about tarps. In relation to the material, tarps can be made of polyethylene, canvas, vinyl, etc. Polyethylene tarps are resistant and waterproof; some are against ultraviolet light treated and they can last for years. Canvas tarps are water resistant but not waterproof: standing water will drip through it. Vinyl tarps are really resistant; they resist oil, acid, grease and mildew and they are water proof.
Thickness is measure in mils or in categories like “regular duty”, “heavy duty”, “super-heavy duty”, etc. The size is usually a little smaller than advertised (usually three to five percent smaller); for example, if the tarp advertise 20ft x 20 ft, it will be actual 19ft x 19 ft. Grommet strength is referred to simple vs. reinforced. Grommet types are aluminum, stainless steel, etc.
If you want to know about the tarp strength, pay attention to the “weave count”: if the number is great so the resistance, especially against ripping in extreme windy conditions; it often runs between 8 and 12 per square inch. Other characteristics that offer tarps are waterproof, mildew proof; and flexibility that make them, more resistant in cold weather.