  In the last years it has been shown that some properties of strongly coupled
superconductors can be potentially described by classical general relativity
living in one higher dimension, which is known as holographic superconductors.
This paper gives a quick and introductory overview of some holographic
superconductor models with s-wave, p-wave and d-wave orders in the literature
from point of view of bottom-up, and summarizes some basic properties of these
holographic models in various regimes. The competition and coexistence of these
superconductivity orders are also studied in these superconductor models.
