Layouts are composed of Bricks
A brick is a sub-template part.
When your layout is Collection (plural), the availables bricks are : Grid, Toolbar, Filters.
Bricks are instanced per default, but you can add/remove as your please.
A toolbar is a wrapper for tasks. Joomla components are using a toolbar object to define and render the possibles operations.
Collection / Plural bricks
Grids are simple lists. Cook is using this term to make difference simply speaking.
Note: A grid brick is created inside a specific sub-template file: ../tmpl/xxxxx_grid.php
All filters are grouped together in a filter brick
Item / Singular bricks
A form is a list of inputs to collect datas from the user.
Note: A grid brick is created inside a specific sub-template file: ../tmpl/xxxxx_form.php
A fly is a simple view or the datas for an item row.
Note: A grid brick is created inside a specific sub-template file: ../tmpl/xxxxx_fly.php
Define a CSS class to apply on the brick wrapper.
Define the alias af the brick.