The overview shows all your tables, queries, forms, reports and scripts at a glance. It is divided into 5 sections. Each section has a list of the corresponding items.
The add button creates a new item. The queries section doesn't have an add button - you must use table data or form data view's "Query" button to create a new query.
The remove button deletes the selected item in the section. You must close all non-overview tabs before attempting to delete an item. It prompts for confirmation beforehand.
The design (rulers) button opens the selected item in design view. This is table design view for tables, table data view for queries and form design view for forms.
The edit (pencil) button opens the selected item in edit view. This is table data view for tables, form data view for forms, report view for reports and the script editor for scripts.
The run button (triangle) executes a script. No console is available when running from outside the script editor, so open the script editor first and then run the script to see a console.
Double clicking on an item will open it in edit mode. Alt-Double Clicking an item will open it in design mode.
You can change the style of the overview in UI preferences. The availiable overview styles are "dark", "light" and "perforated" (default).