An Expert Advisor (EA) is an automated trading system used primarily in forex and other financial markets, designed to execute trades based on predefined criteria and algorithms. EAs are programmed using a scripting language like MQL4 or MQL5, which allows traders to automate their trading strategies, manage risk, and optimize performance without the need for constant manual intervention. This technology can analyze market conditions and execute trades 24/7, making it popular among both novice and experienced traders looking to enhance their trading efficiency.