

I wouldn’t be able to tell you more than it’s an updated version with some new features added…
According to Wikipedia:
Windows 98 Second Edition (often shortened to Windows 98 SE and sometimes to Win98 SE or 98 SE)[76] is an updated version of Windows 98 released on June 10, 1999, about eight months before the release of the business-oriented Windows 2000.[77] It includes many bug fixes,[78] improved WDM audio and modem support, improved USB support,[76] added SSE2 support, the replacement of Internet Explorer 4.0 with Internet Explorer 5.0,[78] Web Folders (WebDAV namespace extension for Windows Explorer),[79] and related shell updates. Also included is basic OHCI-compliant FireWire DV camcorder support (MSDV class driver) and SBP-2 support for mass storage class devices.[80] Wake-On-LAN reenables suspended networked computers due to network activity, and Internet Connection Sharing allows multiple networked client computers to share an Internet connection via a single host computer.[78]
Other features in the update include DirectX 6.1 which introduced major improvements to DirectSound and the introduction of DirectMusic,[78] improvements to Asynchronous Transfer Mode support (IP/ATM, PPP/ATM and WinSock 2/ATM support), Windows Media Player 6.1 replacing the older Media Player 4.1,[76] Microsoft NetMeeting 3.0,[81] MDAC 2.1 and WMI. A memory overflow issue was resolved in which earlier versions of Windows 98 would crash most systems if left running for 49.7 days (equal to 232 milliseconds); this bug was also present on its predecessor, Windows 95.[82] Windows 98 SE could be obtained as retail upgrade and full version packages, as well as OEM and a Second Edition Updates Disc for existing Windows 98 users. USB audio device class support is present from Windows 98 SE onwards. Windows 98 Second Edition improved WDM support in general for all devices, and it introduced support for WDM for modems (and therefore USB modems and virtual COM ports). However, Microsoft driver support for both USB printers and USB mass-storage device class is not available for Windows 98.
Removed features
The Active Channels Channel bar from the original release of Windows 98 is not installed upon first boot, however it is retained when upgrading from the original release of Windows 98 to Windows 98 Second Edition.
Windows 98 Second Edition did not ship with the WinG API or RealPlayer 4.0, unlike the original release of Windows 98, due to both of these having been superseded by DirectX and Windows Media Player, respectively. On the other hand, ActiveMovie still exists in Windows 98 Second Edition despite having been superseded by Windows Media Player.
I suggest spitting to lose weight