Why is login page important?
The login form gives access to your website or web application and therefore to your data. This form fulfills a fundamental task of security; but many times it is omitted to evaluate if the procedures of user name (user), keys (passwords) and authentication comply with the security recommendations.
What is login in app?
A login application is the screen asking your credentials to login to some particular application. You might have seen it when logging into facebook,twitter e.t.c.