Resource tagging is a method of assigning metadata to cloud resources, such as virtual machines, storage volumes, databases, or networks. Resource tags are key-value pairs that can be used for various purposes, such as identifying, organizing, grouping, filtering, or reporting on cloud resources. Resource tagging can also be used for billing recognition, which means tracking and allocating the costs of cloud resources to different departments, projects, or customers. By applying resource tags to cloud resources, department members can provision their own cloud resources and have their usage and costs automatically attributed to their department. Resource tags can also help department managers monitor and optimize their cloud spending, and enforce policies and budgets for their cloud resources. Sandboxing, BYOL, and reserved instances are not related to billing recognition. Sandboxing is a technique of creating isolated environments for testing or experimenting with cloud resources, without affecting the production environment. BYOL stands for bring your own license, which means using an existing software license for a cloud service, instead of purchasing a new license from the cloud provider. Reserved instances are a type of cloud pricing model that offers discounted rates for committing to a certain amount of cloud resources for a specific period of time. Reference: CompTIA Cloud Essentials+ CLO-002 Study Guide, Chapter 3: Cloud Business Principles, Section 3.4: Cloud Billing and Cost Management, Page 891 and Resource tagging best practices | Google Cloud