Technically speaking, garb is just clothing, a uniform, fabric, or any other apparel used to cover the body. However, Wiccan author Deborah Blake uses the term to describe special witchy clothing worn during ritual. This can be anything from a hooded robe to a particular dress to even a vampire cape, if that's your thing. She uses the word "garb" to apply to anything that you don't wear for mundane purposes, even if it is just regular clothing. The idea is that changing into something special puts you in the right mindset for ritual, and further separates you from the everyday.
Given that I'm the kind of witch that actually cuts things with my athame, it's probably comes as no surprise that I don't usually bother with garb. I like the idea of it, but then every time I buy something to wear that I think I'm going to save strictly for ritual, I end up wearing it one or two times just because I like it and it's something new, and then the whole point seems moot.
One way that I've gotten around this is with jewelry. It's easy and inexpensive for me to put together a magical necklace with a moon, pentacle, or goddess charm and a chain or a string of beads. Then, when I make a new one, I can retire the old necklace to my jewelry box to be worn whenever I like. I also find that magical jewelry like this travels well and is quick and easy to throw on, which is great if you like to do a lot of spontaneous ritual like I do. Also, garb in the form of jewelry is really your only option if you practice skyclad!
What are your feelings on garb? Do you think it is strictly necessary? Do you only wear it for certain occasions? Does it have to be a robe or specific costume, or can it be street wear? What color/texture/fabric is it? Are there things you feel you are not supposed to wear? Is this mandated by your tradition, or personal beliefs? Any comments you want to leave on the subject of garb (or lack thereof) will be appreciated, as I think it's a fascinating topic since what we wear is so intimately tied to who we are as individuals.