An expert advisor (also known as an expert adviser, EA, trading robot, etc.) is a trading algorithm written in the MQL programming language. The EA can place, modify, and close orders. Indicators are commonly used by EAs to generate trading signals. These indicators can be standard MetaTrader indicators or custom indicators.
Trading Signals is a trading service that automates the copying of trading operations from one trading account to another. When a trader subscribes to such signals, the same transactions are executed on their accounts automatically.