Use this page to customize the page for you. You can customize the overview layout, menu items, setting default values and queryable fields. If you are a power user then you can customize the detail layout and change filed properties such as mandatory and read only. Your customization can be overridden by the application logic. For an example, a field which you set to editable can be still read-only if the application logic set it to read-only due to certain conditions. Please not that the changes will NOT take effect until the underlying page is refreshed.
For the description of each tab in the page, follow the appropriate link:
Detail Layout,
Overview Layout,
Templates,
Mandatory,
Query,
Read Only,
Menu Items,
F1 Properties.