Wings of Flying are a type of very useful enchanted cloak (they appear in the AD&D Dungeon Master's Guide, but I am really expanding that information by quite a bit).
Wings of Flying appear as a normal cloak of good quality. Most of them are black, although they have appeared in nearly every color known to man. There will be a single command word stitched somewhere inside the cloak. This will often be written in a forgotten language that will take an expert or a mage to decipher. Speaking this word aloud activates the cloaks power. Only the wearer of the cloak can activate it, you can't just yell the command word and activate your buddy's cloak, no matter how funny that might be.
When activated the cloak will cling to the wearer's back and transform into a pair of wings. The exact type of wings will vary, but they are always the same general color as the cloak. For example, a black cloak could produce bat wings, while a white cloak may produce feathered wings. These wings actually attach themselves to the wearer's body (ripping through clothes and armor to do so). They become a part of the user for their duration. It is best to construct a special outfit or suit of armor for use with these wings (with holes in the back), so you don't end up ripping up an outfit every time you use them.
The wings react as if they were another set of limbs on the user's body, so they take a little practice to use. They can be used for up to an hour and a half a day, but this time is reduced for faster flight (they only hold out for about 20 minutes at maximum velocity). The human body is not really designed for wings, using these requires a large amount of effort from the user. After any use of more than ten minutes, the wearer must rest for at least an hour to avoid collapsing from exhaustion.
These wings are best used for escape from hazardous situations, or for dropping bombs/torches/etc on enemies during wartime. Their limited daily usage makes them of little use for long distance travel.
This is only my interpretation of this item, which is based loosely upon its use in the older versions of the Dungeons & Dragons series of games. Your Wings of Flying may be totally different, so always be sure and read the instructions.