This shows Vamana's automatically-sized virtual keyboard (aka "soft keyboard", or "screen keyboard").
The grey/beige keys generate the characters defined in ISO 15919, the international standard for Latin-alphabet transliteration ("Roman transliteration") of South Asian scripts.
The blue keys generate other Unicode characters that are not defined in ISO 15919, but may come in handy during indological work. Vamana also fully covers the IAST standard, an older de-facto standard for Sanskrit in transliteration.
When you click on one of these keys using your mouse, a precomposed character is placed in the text area above. Precomposed characters are ready-made characters which contain all diacritics WITHIN. So when you print them, or when you copy-and-paste them into another software package (such as Word, OpenOffice, or an e-mail program etc.), the characters stay right where they are. No diacritics float around, and everything looks exactly as in Vamana. And: everything remains the same, even if you copy the text to an entirely different operating system!
Vamana is 100% Unicode-compliant, so all keys produce Unicode characters (fully documented). Vamana saves texts in Unicode text format (UTF-8, UTF-16). So Vamana-created texts can be put online on a website without any further conversions.