Simply a Double sided tape is a pressure-sensitive tape coated with adhesive on both sides. The primary function is to bond two surfaces together allowing the end user to replace the use of mechanical fixings without compromising on performance or strength. This can give a neat looking finish to most applications, reduce labour intensive work and offer an alternative solution to many end users. There are double sided tapes for almost any industry and application. For a more detailed explanation, please have a look at this link on wikipedia