If someone asks you this they’re probably actually asking you some combination of these 3 questions:
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 Let's go through them.

Vocaloid (ボーカロイド, Bōkaroido) is a singing voice synthesizer software product developed by Yamaha. You know how if you don’t own a piano you go and use a piano synth to synthesize a piano? Same thing as that, but for vocals. You input words and notes and out comes the Singing Voice from the Voicebank. You can choose different voicebanks for different voice types, and adjust these parameters to get the sound to how you want. That's basically it.

The Vocaloid program currently has 6 editions and currently about 80 voicebanks you can use with them. Some of these voicebanks come with character avatars to help them sell, some of which are these fun anime characters.

no.

Siri is an example of Text To Speech software, which is a voice synthesizer, but it’s not Vocaloid. "Vocaloid" is the name of a specific software product, not a generic term that describes voice synthesizers. like how “Coke” is one brand of soda, not actually a broad term to refer to soda generically.

Well there’s plenty of possible reasons:

Can't sing
Don't have the money for vocalists
Don't have the voice type they want
Vocaloid cool
Miku cute

That brings us to question 2:

This is a lot more nuanced. Basically, y’know those fun anime character avatars that come with these voicebanks? People got pretty attached to those characters, to the point of actually wanting to write songs FOR them, and it’s grown from there.
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Since 2007 or so, the Vocaloid fandom has continued to grow and evolve, with producers coming and leaving the scene. A lot of music producers you might have heard of actually started in Vocaloid such as Kenshi Yonezu and Ayase (YOASOBI Composer).

 The songs are made by human music producers that use the Vocaloid program. In this sense, it’s essentially an instrument. Attributing a song to a Vocaloid is the same as if you attributed Moonlight Sonata to "Piano". Let’s properly credit producers!

 You’re probably asking not about the Software, but about the character.

Hatsune Miku is the avatar character for the Hatsune Miku voicebank developed by Crypton Future Media. She is not the first Vocaloid, but she’s the biggest and started Vocaloid’s huge popularity. But if you’re actually asking about her as a character, here’s her character:

Age: 16 Years⠀⠀⠀⠀⠀       
Height: 158 cm / 5 ft 2 in⠀⠀⠀⠀       
Weight:42 kg / 93 lb


It’s literally whatever you want it to be. Her “personality” you know is more or less crowdsourced. Like how popular fanon becomes canon in normal fanbases, except Vocaloid doesn't actually have a canon, so it’s all just fanon (It's free real estate). There’s a lot more to each of these questions to go into, but hopefully this was a helpful brief overview. Thanks


  1. What is Vocaloid (the software)
A singing voice synthesizer product by Yamaha.

  2. What is Vocaloid (the culture)
People like the voicebank character avatars and make content for them.

  3. Who is Hatsune Miku
The most popular Vocaloid. No canon personality, making her a "crowd-sourced virutal idol"