This is kinda unusual scientific calculator.
What makes it unusual is that you can see both sides of the current binary operation. For example -- if you type 2 + 2 you'll see exactly "2 + 2" until you press "=". The tool was made with touch-screen in mind and is optimized for small devices (10" tablets and netbooks).
The way it works (showing both left and right operand at the same time) means that if you have an operation entered (for example: 5 * 6) and tap some unary operation button (for example the square button) the operation will be performed on the second operand (in our example 6 will become 36).
On devices with keyboard you can use the obvious keys: number keys, dot (floating point), +, -, *, /, Enter (=), ESC (C) and BackSpace. The advanced ("scientific") functions are not yet accessible with keyboard shortcuts (but better keyboard support is planned for the next release).