(a) An ether is an oxygen bridge between two organic compounds.
For example: R-O-R'
(b) An alcohol is a special case of an ether, one in which one R is replaced with a hydrogen (for that matter, water could very well be considered to be an ether in which both R groups are replaced with hydrogens, though in this latter case one would no longer be referring to a organic compound).
(c) Conversely, the hydrogen of a hydroxyl group may be replaced with a organic compound. It occurs when two alcohols join through the loss of a water molecule in a reaction called dehydration synthesis: R-OH + HO-R' --> R-O-R' + HOH