what is difference between regular duct tape & military duct tape? I am confused.

Think that a better question would be what is the difference between good duct tape and cheap duct tape. The cheap duct tapes are usually thinner and not as sticky. The better tapes have thicker backing, are more durable and have a lot more sticky stuff on them.

Have used the military tape and it is a nice heavy duty duct tape that is not silver. If you are looking to buy a good tape at your local building supply the tapes that are in the $10-$15 range are usually good tapes. My personal favorite is Nashua 357. Have also heard that the gorilla tape (think that it is black not silver) is good also but i have not tried any yet.

If you want to use it temporarily you can also get gaffer tape, it is a little harder to find than duct tape but it does not leave a residue behind. Think that the last time i was at the photo shop they had it for almost $30 a roll. Glad i didn't need any. hth.

Is military duct tape tough ? is it as strong as gorilla duct tape ?

There is essentially no difference between military grades and top quality commercial grades of duct tape. They are made by the same manufacturers and in the same factories. Many of the professional grade duct tapes carry a mil-spec specification code rating. Checking the label for specifications and approvals, sometimes also found printed inside the cardboard core, and going by price are two good ways of estimating the grade of tape.

I have found that the big-box hardware stores that cater to contractors, like Home Depot and Builder Square, carry a wide variety of grades of 'Duct Tape'. I use the quotes because the one thing you don't use 'duct tape' on is air ducts. On ducts you use foil tape.

The difference between discount store grades($3-5)and high quality commercial grades($9-17)is quite remarkable. The cheap stuff often falls off in a day or two on its own. In the cold it may not stick at all and in summer heat the stickum may smear, run, make a mess and generally be more trouble than something that just fails to work.

Cheaper grades don't store well and will deteriorate to uselessness in a few months even in near ideal storage conditions. High quality tape lasts longer even when stored in difficult conditions. The roll of good stuff, $15, I keep in my trucks cross-bed tool box is blasted and baked by the Florida heat but even after a year and more of this abuse it still works well.

My advice is to avoid the duct tape advertised as mil-spec. Most of it is just good quality commercial grade tape hyped by associating it with the military and sold at three times the price. If OD green is what you want Granger will sell you good quality stuff in OD green. They also carry black, blue and white if those colors suit you. All the same stuff. Just different colors.

On many jobs, particularly when permanence is important and where heat and moisture are present, foil tape is a better choice than even top quality duct tape. There is even a ultra-high grade foil tape made with stainless steel foil instead of the more usual aluminum. Seal an item, like a small bundle of matches wrapped in wax paper tinder, between two pieces of foil tape and it is protected from water and air pretty much forever.