I am getting a Validation Error on my Project Schematics what does this mean

When validating schematics in a Project, various messages can be generated by the compiler. Please review the list of messages provided here for more information

Starting in Version: 18.0
Up to Version: Current

Solution Details

Where can I find a comprehensive list of compile errors?

When validating a project, an Electric Rule Check, ERC, is performed. This check will report violations based on the project options specified in the 'Project ► Project Options' under the Error Reporting and the Connection Matrix tabs. A detailed reference, Project Compiler Error Reference describes all the compiler errors along with details on how to resolve issues.

https://www.altium.com/documentation/altium-designer/project-compiler-violations-reference-ad

Note: 

In versions of the software prior to Altium Designer 20.0, the project had to be manually compiled to build the Unified Data Model. Since then, the design data model is incrementally updated after each user operation through dynamic compilation - creating what is referred to as the Dynamic Data Model (DDM). There is no manual compilation of the project involved, it is all done automatically.

The process of validating is integral to producing a valid netlist for a project. Connectivity awareness in your schematic diagram can be verified during compilation according to rules defined as part of the options for the design project - on the Error Reporting and Connection Matrix tabs respectively.