BI analyst's main role in a company is to get the requirements from the stakeholders. Then, come up with different strategies and solutions which meet those requirements. BI analysts should have a good understanding of the business domain. They have to make useful insights from the data and make decisions that improve the business of the company. They also have to analyze the after-effects of implementing the solution.
If you are interested in becoming a BI analyst, I would suggest you enroll in Business Intelligence Master's Program by intellipaat.
Here is a video you can check out to find out more about the responsibilities of BI analyst: