Textures of artificial hair  vary from very straight to extremely curly or kinky. The exact names of curl patterns vary by brand, and the possibilities of curl patterns with synthetic wigs are endless, but textures of some packaged examples include:
Silky Straight - Straight and smooth, East Asian hair.
Yaki wigs- Straight, usually mimicking the texture of relaxed Afro-Caribbean hair.
European - Straight European hair; less straight than Asian hair. May be has a tiny amount of wave.
Deep Wave - While generally not a true 'wave', it can be made to look like spiral curls.
Loose Deep Wave or Romance Wave - Looser version of the deep wave, softer, more romantic curls.