PT Mono, as its name indicates, is a monospaced font, meaning that every character occupies the same amount of same along its horizontal axis. Its evenly spaced characters makes it ideal for writing programming language. That also makes it super easy to read on the screen, though it may not be the best choice for non-technical texts.
best used for
COMBINes well with
+ Example: Oswald and PT Mono via Beautiful Web Type