Mail merge is a computer process that allows for the creation of personalized documents, such as letters or emails, by merging a template with a database of recipient information. This efficient and time-saving technique eliminates the need for manually typing out individual documents, making it a valuable tool for businesses and organizations. With mail merge, each document can be customized with specific details, such as names, addresses, and other relevant information, making it a powerful tool for creating personalized and professional communications.