To the wide variety of CSS selectors, jQuery adds its own custom selectors. These custom selectors enhance the already impressive capabilities of CSS selectors to locate page elements in new ways.
When possible, jQuery uses the native DOM selector engine of the browser to find elements. This extremely fast approach is not possible when custom jQuery selectors are used. For this reason, it is recommended to avoid frequent use of custom selectors when a native option is available and performance is very important.
Most of the custom selectors allow us to choose one or more elements from a collection of elements that we have already found. The custom selector syntax is the same as the CSS pseudo-class syntax, where ...