The Strategy Tester is a built-in tool in MetaTrader that allows you to test trading strategies and optimize the settings of Expert Advisors (EAs). During backtesting, the tester simulates the EA’s performance using historical data, which helps assess its profitability and potential risks over a specific past period.

In optimization, the tester runs multiple simulations with different parameter sets to find the optimal settings that produce results matching your expectations. This way, you can fine-tune your EA for better performance.

For a more detailed analysis of the results, it's best to consult with the developers of the EA or robot to understand the performance nuances fully.