the meaning of sirens

I know I am late but I was busy, so I found the meaning on http://www.mythicalcreaturesguide.com/page/Siren 

I am hooked on the meaning of siren and what will happen...

I remember reading somewhere that someone said they were not sea nymphs but this proves it.

But I thought that nymphs were good like Daphne?

Here's the meaning:

In Greek mythology the Sirens or Seirenes (Greek Σειρῆνας) were Naiads (sea nymphs) who lived on an island called Sirenum scopuli, or in some different traditions,some place them on cape Pelorum others in the island of Anthemusa, and others again in the Sirenusian islands near Paestum, or in Capreae which was surrounded by cliffs and rocks. Approaching sailors were drawn to them by their enchanting singing, causing them to sail into the cliffs and drown. They were considered the daughters of Achelous or Phorcys. Homer says nothing of their number, but later writers mention both their names and number ; some state that they were two, Aglaopheme and Thelxiepeia; and others, that there were three, Peisinoe, Aglaope, and Thelxiepeia or Parthenope, Ligeia, and Leucosia. Their number is variously reported as between two and five, and their individual names as Thelxiepia/Thelxiope/Thelxinoe, Molpe, Aglaophonos/Aglaope, Pisinoe/Peisinoë, Parthenope, Ligeia, Leucosia, Raidne, and Teles. According to some versions, they were playmates of young Persephone and were changed into the monsters of lore by Demeter for failing to intervene when Persephone was abducted. The term "siren song" refers to an appeal that is hard to resist but that, if heeded, will lead to a bad result.

Within the tales of Greek Mythology there were a couple documented cases where the siren song was thwarted. The first were the Argonauts whom had Orpheus play a tune louder than they, the second was Odysseus' men who plugged their ears with beeswax. Odysseus alone volunteered to hear the song whilst tied to the ship's mast. This second escape resulted in the Siren's killing themselves out of shame. It was because of this that later writers would say the Siren's were fated to die should a person hear their song and escape unharmed.