What is Business Analysis?
Business Analysis is an activity which helps to introduce/initiate change in an organization, process, functioning, software etc. by identifying needs, collecting detailed input, analyzing the requirement, analyzing and forecasting the impact of the change on the system and recommending solutions that would deliver value to the end users. These activities are carried out through certain tasks and techniques which are defined in various books the prominent being BABOK(Business Analysis Book Of Knowledge).
Who is a Business Analyst?
A Business Analyst is a person who initiates/studies, suggests and implements changes in an existing system or in some cases in an evolving system. This activity is carried out with the help of the stakeholders who are directly or indirectly affected by the change. The business analysis activity does not only includes functions of a business analyst but also includes activities carried out by business system analyst, system analyst, requirement engineer, process analyst, product manager, product owner, enterprise analyst business architect, management consultant, business intelligence analyst, data scientist and many more such functioning.
Many functions, department and roles in a business such as management, project management, product management, software development, quality assurance and interaction design depend heavily on business analysis for their success.

How does Business Analysis help? Or How does Business Analysis work?
Business Analysis is a structured approach for initiating and managing changes to organization, whether they are for profit business, government, or non-profits. It is used to identify and communicate the need for change in functioning of an organization and to facilitate that change.
A Business Analyst who carry out Business Analysis is a key player and is a creator or agent of change. They identify and define solutions that will maximize the benefit provided by an organization to its stakeholders.
Business Analysis work across all levels of an organization and could be involved in all processes right from defining strategy, to creating the enterprise architecture, to taking a leadership role by defining the goals and requirements for programs and projects or supporting continuous improvement in its technology and process. They have the know how to handhold and lead the business through the unknown and get the desired results
Business Analysis ensures , highlighting and achieving benefits, curtailing or avoiding unnecessary costs, identifying new opportunities, understanding of required capabilities and modeling the organization, ultimately improving the way business needs to be carried out.