Actually, it's more like a minefield.
Avatar appearance in Second Life used to be pretty straightforward. Way back at the beginning, you just used the Appearance sliders to change everything. If you wanted a new shirt or pants or skirt, you created a texture in Photoshop, uploaded it, and applied it in the Appearance window. If you wanted to change your shape, the Appearance sliders were what you used. If you wanted different makeup or hair, well, there were Appearance sliders for that, too.
But Second Life residents are endlessly inventive, and kept looking for ways to improve on the look that was available with the Appearance sliders.
First came fully painted, detailed skins. These could not be modified with Appearance makeup sliders, so creators offered them in "fatpacks" with an assortment of makeup choices.
But for some, five or six or eight makeups wasn't enough. So when the Tattoo layer was introduced, along came makeup tattoos that could be applied over the skin.
The ugly "system hair" was replaced by much prettier prim hair (although system hair is still around, in the form of the mandatory "bald head" body part.) Then hair became flexible, when flexiprims were introduced. Mesh hairstyles took away the flex, but created hair that didn't penetrate our shoulders.
Bodies became more flexible, first with the system introduced in the old Emerald viewer (which later evolved into Phoenix and then Firestorm) and then in the stock viewer with the addition of the "physics" clothing layer.
Fingernails evolved. First there were nails painted on the glove clothing layer, and later on the tattoo layer. Then someone invented prim nails, which were much more crisp and detailed than the glove layer nails...but tended to "pop off" in certain hand poses. When Mesh was introduced, we got whole hands and feet, with the nails built in and adjustable with texture "appliers." Now, in fact, it's getting harder to find shoes that are NOT made for the wildly popular SLink mesh feet.
Speaking of feet, when sculpties were introduced, we got pretty shoes for the first time. Then the creators started making shoes with integral feet (which I must admit, looked a lot better than the clubs that come with the standard avatar.)
Soon, prim attachments, then sculpted prim attachments, supplemented clothing layers, making clothing much more realistic...but also more complex. A shirt might require not only a shirt layer, but attachments for collar, shirttail, front ruffles, and poofy sleeves or cuffs.
Then Mesh clothing came along. Since it wasn't resizable like the old clothes, we now had to worry about "what size will fit me?" And even if we wore a "standard mesh" shape, nothing was guaranteed. An alpha layer was almost always needed in addition to the mesh clothing item, and even when Fitted Mesh came along, the alpha was still a requirement to keep us inside our mesh clothes.
Shoes used to hide the avatar foot with "invisiprims" but when Alpha mask layers were introduced, those became obsolete. Alphas look much better, but you do have to pay attention and manage your alpha layers. You can have one for your shoes, another for a skirt, a third for a top, another for your head, and yet another for your mesh hands. You're maxed out at five.
Girls who wanted a more voluptuous figure were accommodated with mesh breasts and buns. But again, these required special attention...texture appliers had to be included with outfits by designers to paint the clothing texture on the mesh attachments.
Oh, what the heck, why not replace the entire avatar with a mesh body? Some of these are very beautiful. But they can't wear standard clothes, or indeed any clothes that are not created to work especially with them.
If you're new to Second Life, nobody can blame you for feeling lost and confused as you try to navigate the complexity of today's avatar appearance choices. Maybe you would feel less stressed if you just put on a Furry avatar and told the clothing designers to take a long walk off a short pier. (Or maybe not. My friend Tali Rosca pointed out to me that Furries have had to deal with all these problems longer than us human avatars, what with all the attachments that make up a Furry avatar!)
Or maybe LL will cut through all this with the design of the new virtual world that may one day replace this messy old Second Life.
You'll have to excuse me...I'm behind on assembling outfits for all the new dresses I just bought!