Hatsune Miku is a vocaloid voicebank and software first created in 2007, created by Crypton Future Media. She is voiced by Saki Fujita. This is her:
Vocaloid is a software that allows the user to create vocals based on the different sounds in a language, specifically, in this instance, Japanese. Miku has become an iconic symbol online, and also is also creditted in songs. She has allowed for people, that are unable to sing their own songs, to have a voice, and it all comes through the voice that Saki Fujita gave to her. There are also other voicebanks with personalities; some created by the same company that created Hatsune Miku, and even some created by fans as an April Fools joke that was taken seriously. So many people have found a voice or been inspired by this fictional character, that she has millions of fans and even goes on concert tours.