本文转自;https://msdn.microsoft.com/en-us/library/hh264221.aspx

A project can be built to run on a target framework, which is a particular version of the .NET Framework, and a target platform, which is a particular software architecture.  For example, you can target an application to run on the .NET Framework 2.0 on a 32-bit platform that is compatible with the 802x86 processor family (“x86”). The combination of target framework and target platform is known as the target context.

A target framework is the particular version of the .NET Framework that your project is built to run on. Specification of a target framework is required because it enables compiler features and assembly references that are exclusive to that version of the framework.

Currently, the following versions of the .NET Framework are available for use:

• The .NET Framework 2.0 (included in Visual Studio 2005)

• The .NET Framework 3.0 (included in Windows Vista)

• The .NET Framework 3.5 (included in Visual Studio 2008)

• The .NET Framework 4 (included in Visual Studio 2010)

• The .NET Framework 4.5 (included in Visual Studio 2012)

• The .NET Framework 4.5.1 (included in Visual Studio 2013)

• The .NET Framework 4.5.2

• The .NET Framework 4.6 (included in Visual Studio 2015)

The versions of the .NET Framework differ from one another in the list of assemblies that each makes available to reference. For example, you cannot build Windows Presentation Foundation (WPF) applications unless your project targets the .NET Framework version 3.0 or above.

The target framework is specified in the TargetFrameworkVersion property in the project file. You can change the target framework for a project by using the project property pages in the Visual Studio integrated development environment (IDE). For more information, see How to: Target a Version of the .NET Framework. The available values for TargetFrameworkVersion are v2.0, v3.0, v3.5, v4.0, v4.5, v4.5.1, v4.5.2, and v4.6.

<TargetFrameworkVersion>v4.0</TargetFrameworkVersion>  

A target profile is a subset of a target framework. For example, the .NET Framework 4 Client profile does not include references to the MSBuild assemblies.

The target profile is specified in the TargetFrameworkProfile property in a project file. You can change the target profile by using the target-framework control in the project property pages in the IDE. For more information, see How to: Target a Version of the .NET Framework.

<TargetFrameworkVersion>v4.0</TargetFrameworkVersion>  <TargetFrameworkProfile>Client</TargetFrameworkProfile>  

A platform is combination of hardware and software that defines a particular runtime environment. For example,

• x86 designates a 32-bit Windows operating system that is running on an Intel 80x86 processor or its equivalent.

• Xbox designates the Microsoft Xbox 360 platform.

A target platform is the particular platform that your project is built to run on. The target platform is specified in the Platform build property in a project file. You can change the target platform by using the project property pages or the Configuration Manager in the IDE.

<PropertyGroup>     <Platform>x86</Platform>  </PropertyGroup>    

A target configuration is a subset of a target platform. For example, the x86``Debug configuration does not include most code optimizations. The target configuration is specified in the Configuration build property in a project file. You can change the target configuration by using the project property pages or the Configuration Manager.

<PropertyGroup>     <Platform>x86</Platform>     <Configuration>Debug</Configuration>  <PropertyGroup>    

[转]MSBuild Target Framework and Target Platform