Perm is the common term for a permanent wave, a hairstyle that curls a person's hair by means of chemical treatments.
The history of the perm is long and uncertain. The first permanent wave might be said to have been invented in 1906 by Karl Nessler. He discovered that if you wrapped hair around hot metal coils and coated it with sodium hydroxide the hair would stay curled for a long time. Despite his apparatus being very unwieldy, very hot, and taking six hours to do its job, it became quite popular.
The perm slowly advanced through the decades, having many problems but many more admirers. In 1938 Arnold F. Willatt invented the cold wave, which was very nearly the same perm that you get at your modern hairdresser. It didn't need any heat or machines, but it could still take up to eight hours to finish the perm. Today a perm takes from 15 minutes to half an hour, and is still amazingly popular.
Before you start a perm, you will need to curl your hair. This is usually done with rollers. When you wet your hair before putting it up in rollers (or heat your hair with the iron) you change the salt bonds and hydrogen bonds that help your hair keep its shape. But these are not the strongest bonds keeping your hair shaped, so the next time you get your hair wet these curls will come out. What we need is something to make it permanent.
This is where the fancy chemicals come in. The strong bond that will pull your hair back to its original form is found in the amino acid cysteine, which forms disulfide bonds. The disulfide bonds are what gives hair its elasticity. A perm works by applying two chemicals; one is the 'waving lotion' which release the disulfide bonds (usually either sodium thioglycolate or ammonium thioglycolate), and the second is a 'neutralizer' which actually reforms the disulfide bonds after the hair has been molded into curls. (These same chemicals can be used to straighten kinky hair.)
A perm can make your hair curlier, give it more body and movement, make it more manageable, make it easier to style, and turn you into a glamorous starlet. You can get various looks depending on the size of the rollers you use, whether you perm all of just part of your hair (it is common to leave the crown of the head unpermed), and whether you are an 80s rocker or not. (Please do not be an 80s rocker).
In general, you can get your hair permed about every six months. More often may damage it, although frequent perms can be okay if your hairdresser knows what she's doing. Let the hairdresser do her job. If the perm is done incorrectly it can make your hair limp and brittle. You should not experiment with home perming if you value your hair. (But quite frankly, your hair is just fine the way it is, and you do not need to do anything to it.)
Perm is also a city in Russia. But I can't help you with that.