Who exactly is Feanor and Celebrimbor?

[Mhoram]

And it was told by the Vanyar who held vigil with the Valar that when the messengers declared to Manwë the answers of Fëanor to his heralds, Manwë wept and bowed his head. But at that last word of Fëanor: that at the least the Noldor should do deeds to live in song for ever, he raised his head, as one that hears a voice far off, and he said: 'So shall it be! Dear-bought those songs shall be accounted, and yet shall be well-bought. For the price could be no other. Thus even as Eru spoke to us shall beauty not before conceived be brought into Eä, and evil yet be good to have been.'
But Mandos said: 'And yet remain evil. To me shall Fëanor come soon.'