The Full Form of MSIE is Microsoft Internet Explorer.

Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical web browsers developed by Microsoft and included in the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year. Later versions were available as free downloads, or in-service packs, and included in the original equipment manufacturer (OEM) service releases of Windows 95 and later versions of Windows. New feature development for the browser was discontinued in 2016 in favour of their new browser Microsoft Edge. Since Internet Explorer is a Windows component and is included in long-term lifecycle versions of Windows such as Windows Server 2019, it will continue to receive security updates until at least 2029. Microsoft announced in August 2020 that as of August 2021, web-based Microsoft 365 products will no longer support Internet Explorer, with support for Microsoft Teams ending earlier in November 2020.