This page is a username generator. It generates syllables with a CV[C] structure, that is, a consonant followed by a vowel and an optional final consonant. For the first syllable, the first consonant is optional as well.
The intent of this tool is to generate names that can be pronounced. It doesn't do an amazing job at that, so you may want to tweak the result a bit.
The source code is available on Github or in your browser, by right-clicking and selecting "View Page Source".