Properties of Copper oxideWatch
Is copper Oxide ionically bonded?
ions are atoms that have charges
so if you have bonding between metals and non-metals, you'll get a charged bond because one receives a negative charge (the electron) and the other gets its negativity taken away (via its election being transferred to the non-metal)
so ionic bonding is the bonding between metals and non-metals (i.e. copper oxide vis-a-vis copper and oxygen)
as for why it is insoluble in water, I can't even remember.