The game color inks I've used actually aren't all that glossy. If you let them pool the pools will tend to be on the glossy side, but overall they're more of a satin or matte finish.
But yeah, inks are a bit like washes but they have much more dense colour to them. They're actually often very thin from a viscosity perspective, but denser in colour. If you want a more subtle effect like you get from a wash you have to thin them, it's usually best to thin with some sort of thinning medium rather than just water to avoid having an excessively high surface tension.
Usually with inks, similar to washes, you paint the model on the bright side and then apply the ink to give it depth and darken it. I sometimes use the model below to show the stark difference between inks and washes. It was painted initially with a light bone colour and then the pale skin areas are done with a brown wash (the old
GW Devlan Mud wash) and then the much deeper brown on the brains and fleshy bits are done using a brown ink. So you can see how much deeper and darker the ink looks.
Just a general note for people buying inks, Game Color, P3 and artists inks are actually inks. Army painter used to label their paints as inks, but they're actually far more like washes than inks. Just looking at the Army painter site it looks like they've corrected their labelling and are now calling them washes.