How does ETrade make money?

I'm curious to understand the financial mechanics behind ETrade's operations. Can you elaborate on the primary revenue streams that contribute to ETrade's profitability? Are there any specific fees or commissions that customers pay when using their services? Additionally, does ETrade engage in any other activities or investments that significantly contribute to their overall earnings? I'm eager to gain a deeper insight into how this financial platform generates revenue and sustains its position in the market.