Within a solution you can define dependencies within solution components. Up until Dynamics 365 for Customer Engagement apps version 9.0 the main purpose of these dependencies was to prevent the deletion of a solution component when another solution component depended on it.
The following image shows the dependencies tab within the web resource form. Dependencies between web resources are set in the top list.

Reference:
https://docs.microsoft.com/en-us/dynamics365/customerengagement/on-premises/developer/web-resource-dependencies