Expert Advisors are software programmed to perform actions in response to certain triggers.
Algotrading and Expert Advisors are directly related to each other, as they are based on technical analysis, mathematical models, and statistics.
You can program the Expert Advisor in such a way as to receive notifications about price changes or market events.
For example, if you want to receive a daily report on your trades and the status of open orders, you can create an Expert Advisor that will send you this information.
Testing on the history will allow you to see how your strategy and Expert Advisor work in the past.