Chunk16:Help screen list Filter
From Joomla! Documentation
Filter. In the upper left corner just above the column headings are a Filter field and two buttons, as shown below:

If you have a large number of items in the list, you can use this filter to find the desired item(s) quickly. Enter either part of the title or an ID number and press 'Search' to display the matching items. You can type in whole words or part of a word. For example, "ooml" will match all titles with the word "Joomla!" in them. Click 'Clear' to reset filtering.