How does E-Trade work?

I'm curious to understand how E-Trade functions as a platform for financial transactions. Can you explain the basic mechanics behind it? What are the key steps involved in setting up an account and initiating trades? How does E-Trade facilitate the buying and selling of stocks, bonds, and other securities? Additionally, what security measures does E-Trade have in place to protect users' funds and personal information? I'm interested in learning more about the technology and infrastructure that powers E-Trade's operations.