Group 1 - The core trading hours for the US stock market are from 9:30 AM to 4:00 PM Eastern Time, with pre-market trading starting at 4:00 AM and after-hours trading ending at 8:00 PM, which differs from domestic trading hours [1] - The US stock market allows for flexible trading units, enabling investors to purchase as few as one share, providing greater flexibility especially for those with smaller capital [1] - The US stock market operates on a T+0 trading system, allowing investors to buy and sell stocks on the same day, which contrasts with the T+1 system in the A-share market [2] Group 2 - Transaction costs in the US stock market include commissions and taxes, with significant variations in commission rates among different brokers, especially with the rise of online brokers offering low or zero commissions [2] - The US stock market features a market maker system that enhances liquidity by providing buy and sell quotes, ensuring timely execution of trades [3] - The US stock market comprises various tiers of stocks, including main board and growth board, each with distinct listing standards and trading rules, necessitating careful selection by investors [3]