I don't know what it was used for. Looks like a cup/bowl. Is it from the qianlong period?
It is more likely from the late Qing dynasty, based on the type of blue pigment used. I have never seen such an item with a high base before, and the color of the foot area inside the foot rim should be the same as elsewhere. If it is different, there is a possibility that this is a repaired or modified item.