What is a markup language primarily used for?

A markup language is primarily utilized for structuring text files for web documents, which includes defining elements such as headings, paragraphs, links, and other webpage components. By using markup languages like HTML (Hypertext Markup Language), developers can create a structured layout that web browsers can interpret and display visually to users. This structure also enhances the accessibility of the content, making it easier for search engines to index and users to navigate.

While other options mentioned may refer to functions of different technologies, they do not apply to what a markup language fundamentally does. Storing data is typically managed by databases, creating graphics and images involves graphic design tools or programming languages geared toward rendering visuals, and encrypting information pertains to security measures, which are not relevant to the purpose of markup languages. Thus, the focus on structuring text files specifically for web documents accurately highlights the primary role of markup languages.