Media → Library
Media consists of the images, video, recordings, and files that you upload and use in your blog. Typically uploaded and inserted into the content when writing a Post or writing a Page. Note that the Uploading Setting in the Settings Screen describes the location and structure of the upload directory (where your files are stored). If you do need to upload items, even if that Media is not related to a Post or Page, then you need to use the Add New Screen.
The Library Screen allows you to edit, view, and delete item previously uploaded to your blog. Multiple Media objects can be selected for deletion. Search and filtering ability is also provided to allow you to find the desired Media.
At the top of Grid View, you can filter the items by media type and date:
- All items
- This dropdown allows you to select, by type such as Images, Audio and Video or Unattached to any Posts nor Pages, which items are displayed in the Table of Media. By default, “All items” is selected and all of your items are displayed.
- All Dates
- This dropdown allows you to select, by date, which items are displayed in the Grid View. By default, “Show all dates” is selected and all of your Media are displayed.
To the right, is a Search box where you can enter a word, or series of words to search and display all the items meeting your search words. The search results will be updated as you type.
To delete items, click the Bulk Select button at the top of the screen. Select any items you wish to delete, then click the Delete Selected button. Clicking the Cancel Selection button takes you back to viewing your items.
Source: read more on Media in WordPress