❔ Why is microsoft.net.test.sdk a nuget?

I am trying to wrap my head around this, but can't seem to find an answer. Why is it that

Microsoft.NET.Sdk.Web

Microsoft.NET.Sdk.Web

can come from a local installation and can be specified in the

<Project>

<Project>

tag, but

Microsoft.NET.Test.Sdk

Microsoft.NET.Test.Sdk

seems to require to be a NuGet?

❔ Why is microsoft.net.test.sdk a nuget? - C#