The "jira-users" group in JIRA is significant because it includes all users with access to the JIRA instance. Users added to this group typically have basic permissions to interact with projects and issues within JIRA. This group is fundamental for granting initial access to new users and ensuring that they can start using JIRA effectively. It is not exclusive to administrators or users with specific license types; rather, it encompasses all users in the JIRA environment.

Project roles in JIRA are collections of users who have common access rights and permissions within a specific project. They help in managing and controlling access to project resources and functionalities based on user roles.

Global Permissions in JIRA are used to control access to system-wide settings such as user management, application access, and administrative functions.

A "permission scheme" in JIRA is a predefined set of rules that determine the actions users or groups of users can perform within a project or instance. These schemes are applied to projects and define permissions for various operations, such as viewing, creating, editing, or deleting issues, managing project configurations, or accessing certain features.

Issue Linking in JIRA allows users to establish relationships or dependencies between different issues. This helps in tracking related tasks, identifying dependencies, and understanding the overall progress of a project. For example, you can link a bug report to the corresponding feature request, or link an epic to its related user stories.

Customizing a workflow in JIRA is essential for tailoring the issue tracking process to match the unique needs and workflows of different projects or teams. This customization enables organizations to streamline their workflows, enforce business rules, and improve overall productivity and collaboration.

The correct option is "Incremental". Sprint Execution involves delivering incremental increments of product functionality, where at the end of each Sprint, a potentially shippable product increment is delivered, adding value to the product.

In JIRA, typical reasons for transitioning an issue from one status to another include completion of a task, need for further review, change in priority, and various other workflow-related actions. All of these options are valid reasons for transitioning an issue.

Permission schemes in JIRA allow project administrators to control access to various project actions, such as creating, editing, or transitioning issues. By assigning appropriate permission schemes, administrators can ensure that only authorized users can perform specific actions within the project.

Users can review and rate JIRA plugins and add-ons on the Atlassian Marketplace. The Atlassian Marketplace serves as a centralized platform where users can find, evaluate, and acquire plugins and add-ons for various Atlassian products, including JIRA.