OST or Offline Storage Files represent user's mailbox data in offline mode on local machine upon registration with Exchange Server using Microsoft Outlook. It is automatically created on the first use of Microsoft Outlook upon connectivity with server. Once the file is created, the data is synchronized with the email server so that it is available offline as well in case of disconnectivity from email server.
WebP, introduced by Google, is a modern raster web image file format that is based on lossless and lossy compression. It provides same image quality while considerably reducing the image size. Since most of the web pages use images as effective representation of data, the use of WebP images in web pages results in faster loading of web pages.
You can also convert OST into many other file formats. Please see the complete list below.