Containers are often touted for their ability to allow applications to "build once, run anywhere," but this claim can be misleading due to environment-specific configuration settings. Kubernetes ConfigMaps address this issue by separating these settings from the containers themselves, enhancing portability without needing to rebuild container images for each environment. ConfigMaps store configuration data in key-value pairs, making it easy to update settings dynamically without redeploying applications. Unlike environment variables, ConfigMaps offer more convenience as they don't require container redeployment for changes. While similar to Kubernetes Secrets, ConfigMaps are intended for non-sensitive data, as they do not encrypt stored information. ConfigMaps' main advantages include decoupling configuration from applications, enabling dynamic updates, and providing centralized configuration management, though they lack built-in version control and encryption. Advanced uses include facilitating application migration between clusters and environments, but best practices like avoiding storing sensitive data in ConfigMaps, documenting ConfigMaps, and using live edits for updates are crucial for maximizing their utility. Tools like groundcover can aid in monitoring ConfigMap-related issues that might affect application performance, thus supporting the "build once, run anywhere" promise.