Final answer:
Step-up to M365 Enterprise E5 licenses are designed to add extra features and capabilities on top of existing licenses in a modular manner, providing additional functionalities like advanced security and analytics.
Step-by-step explanation:
When we talk about step-up to M365 Enterprise E5 licenses being additive, we mean that these licenses are designed to add functionality on top of existing licenses without replacing them. In the context of Microsoft 365, an E5 step-up license would typically provide additional features such as advanced security, compliance tools, and analytics over the lower-tier E3 licenses, for instance. This allows organizations to enhance their capabilities in a modular fashion, only adding what they need while maintaining their base license.