Bitcoin open source web wallet with Bitcoin wallet service Where the user email and password are stored when user registered on the web wallet websites like blockchain.com ?

Is the blockchain.com directly interact with the bitcoin blockchain and store the email and password on blockchain ??

How the web wallet works ? How they are interact with the blockchain ?

Sorry for lots of questions in one , The main thing that i want to understand how the more secured web wallet interact with blockchain ?
Where the user email and password are stored when user registered on
  the web wallet websites like blockchain.com ?


In the ORDBMS database.


  Is the blockchain.com directly interact with the bitcoin blockchain
  and store the email and password on blockchain ??


The blockchain.com has full bitcoin node and interact directly with bitcoin node. They doesnt store users data(email, passwords and so on) in the blockchain


  How the web wallet works ? How they are interact with the blockchain ?


Web wallets is a plain middleware between full nodes and users, they are in the cloud.


  How the more secured web wallet interact with blockchain ?


Your wallet is protected, but there is always a chance what this web wallet(or any other web service which offers web wallets) will be hacked.