A native package contains native binaries instead of managed assemblies, allowing it to be used within C++ (or similar) projects. (See Native C++ Packages in the Consume section.)
To be consumable in a C++ project, a package must target the native framework. At present there are not any version numbers associated with this framework as NuGet treats all C++ projects the same.
Note
Be sure to include native in the <tags> section of your .nuspec to help other developers find your package by searching on that tag.
Native NuGet packages targeting native then provide files in \build, \content, and \tools folders; \lib is not used in this case (NuGet cannot directly add references to a C++ project). A package may also include targets and props files in \build that NuGet will automatically import into projects that consume the package. Those files must be named the same as the package ID with the .targets and/or .props extensions. For example, the Microsoft.Web.WebView2 package includes a Microsoft.Web.WebView2.targets file in its \build folder.
The \build folder can be used for all NuGet packages and not just native packages. The \build folder respects target frameworks just like the \content, \lib, and \tools folders. This means you can create a \build\net40 folder and a \build\net45 folder and NuGet will import the appropriate props and targets files into the project. (Use of PowerShell scripts to import MSBuild targets is not needed.)
Create a .NET project and learn to add packages and manage package dependencies in your project. Use the .NET Core CLI and NuGet registry to add libraries and tools to your C# applications through Visual Studio Code.