what is difference between installshield and windowsinstaller
InstallShield (and others, such as Advanced Installer and InstallAware) are tools that help you as the developer create Windows Installation Packages (MSI files). Visual Studio also has the ability to produce MSI files as well, though some find that some features are lacking with the Visual Studio tool.
Wikipedia has a fairly nice article on the subject that you may find interesting.
Windows Installer is included in Windows Operating Systems.
The general idea is that you as the developer package your software (executable and other dependencies) inside an MSI file that the end-user can then use to install the product on their computers via Windows Installer.
There's a lot more to the subject as you'll find as you get more involved with creating, testing and debugging MSIs.
MSI is a platform service provide by Windows. It uses a relational database (.MSI) to express the behavior of an installer.
InstallShield is a brand name and can refer to any number of products and project types. MSI is the output of one or more of the project types supported by InstallShield Limited Edition, Express, Professional and Premiere.
Other tools such as Windows Installer XML (WiX) can generate MSIs as well and tools like wixpie and wixedit can help.
Windows Installer is a service of the Windows operating systems and it comes as a part of any recent version of Windows. The purpose of the Windows Installer is to enable the installation, update, or servicing (i.e. repair) of applications that have been developed to run on Windows. If you are the developer of an application that targets Windows, then you can consider providing your application to users as a Windows Installer package to leverage the capabilities of Windows Installer to deploy and service your application. The Windows Installer service is documented online in the desktop developer center: Windows Installer
Windows Installer is for desktop applications and is NOT the technology used to install Windows Store applications.
A Windows Installer package has the .msi extension, and you will also see Windows Installer referred to as "MSI." Although an editing tool is included in the SDK it is difficult to use, most developers prefer to use a third-party MSI package creation tool. InstallShield is a very popular tool and this and other tools are discussed and compared at length at this InStallSite website. WiX is an open-source authoring tool that is available at SourceForge site.
You should probably look at both the documentation for the tools and the underlying Windows Installer service when considering which is the best tool for your project.