Gouache is a water medium paint. The binder is gum arabic which is sap from acacia trees in some parts of Africa. Gum arabic first found its way to Europe via Arabic ports, so retained its name according to Wikipedia. The paint is opaque and that is a key difference from aquarelle colours or watercolour. For the most part I use artist quality Gouache from Schmicke and some expensive brushes and some very cheap ones as well.
I find working with gouache suits my drawing style. There’s not a whole lot of rules with gouache and you can mix with other materials such as watercolour, pastel colours, coloured pencils, gold leaf or the good old pencil. You can draw with gouache with a reed pen or the dipping pen and if the pigments are fine enough you can use an airbrush as well.
I experiment a lot with gouache and try not to be too frustrated when a painting goes haywire. Like most of my ideas regarding drawing I need to put it down on paper to see if it works and sometimes it doesn’t. No shame in that.