> The Silmarillion
The Edain (eey-die-n, plural of Adan) were the second Children of Ilúvatar to enter Middle-Earth, hence the meaning of the name: the 'second-comers'. They were mortal Men and had three original houses, The House of Bëor, The House of Hador, and The House of Haladin. Only Bëor's house official allied with any of the houses of the Elves, but all of the Edain were great friends of the Eldar.
When they first awakened in Middle-Earth they headed west towards the light of the Blessed Lands. On this journey they entered the lands of Beleriand and joined with the Elves there. Some, however, did not take up this exact journey and either remained where they were or fled south away from Morgoth. A great number of the Edain were slain by Morgoth until Eärendil sailed to Aman and recieved the mercy of the Valar.
The Edain that went into Beleriand lived in harmony and bliss with the Elves there. Their lifespans were increased, they grew stronger and fairer, and they started powerful alliances with their Eldar friends. From this friendship came the two marriages of Men and Elf: Beren and Luthien and Tuor and Idril.