an XML file used to define a QGIS layer style.
The QML (.qml) file in QGIS is a style file. It contains an export of the style information, including labels, from a layer.
Setting up symbology can be time consuming; an alternative is to make use of a pre-defined symbology definitions.
QGIS allows layer style files (.qml) and styled layer descriptor (.sld) files to be loaded allowing us to make use of pre-defined styles.
