[manigandham]

It's basic fingerprinting used by every major security-sensitive service, like banks.

The more entropy (unique bits of data) about your browser context they can collect, the easier it is to recognize you and see if you're a human or not (and block if they need to).

[zaphirplane]

What do you mean? I can use a browser incognito mode and still login

[manigandham]

It's a security measure to see if you're logging in under strange circumstances or an automated browser using stolen credentials or something. Some sites will ask security questions only if they see a new device or IP or geolocation, for example. Incognito just means empty cache and cookies, that's not that suspicious on it's own given all the other details.