A

Alias

Alias term is used in different contexts, we can say an alias is always a safe URL sring. (also called 'slug')

Alias wizard is a builder feature that allows you to automatically create a safe URL / slug string From a field to another.

Alias item / Table alias / Project alias : see plural, see singular

Wizzard / Alias item / Table Alias / Project alias ...

Aliased path

An aliased path is a complete file path using a directory alias.

ex: [DIR_FILES_IMAGE]/2014-03/myimage.png

learn more here

B

Back, back-end

see Client

Brick

a brick is a sub template.
When you call a view, the template is the main scaffolding of the page to render.
Then this template file ex : default.php is calling su templates such as default_grid.php.
In this previous example, grid is the brick.
In the builder, the bricks can be : a toolbar, filters container, grid, form, fly.

Brickfield

a brickfield is an instance of a field inside a brick.
The field can be a Foreing key field picked up from the fields tree in the builder.

Builder

The builder is the Cook Self Service drag'n'drop application, for building your components.
docs : the builder 

C

Client

The client is the user's interface access. In joomla it can be:

front-end : Administrator interface
back-end : Website view for users

D

Directory alias

A directory alias is used to hide the full path of a file.

ex: [DIR_FILES_IMAGE] or [COM_MEDIA]

see full explaination here

F

Front, front-end

see Client

I

Item

An item is the respresentation of an object. It is commonly a row table, but it can be complex object structure.

L

List, Collection, Plural

A list is a view of a collection of items 

M

Manifest

The manifest is the XML installation file of your component.
It describe the name, the author, the version, and some description of the package

P

Plural

Files are distincted if they work/represent list or item.
Plural is used to label lists (files, models, controllers, views, ...)

ex : items / item
items is the plural

Project

The project is representing your component

docs : project

PTL

Project / Table / Layout

This is oftenly asked when you post a support ticket on the forum.
These 3 titles help the admin to localise the concerned page context of your problem.

S

Singular

Files are distincted if they work/represent list or item.
Singular is used to label items (files, models, controllers, views, ...)

ex : items / item
item is the singular 

Slug

see alias

T

Title

Titltes are the translated label string used for rendering. Always name correcly your objects in the builder. Case, spaces and special chars are allowed here.

ex :
title : My Products
alias : products
title item : Product
alias item : product

Triad

in the builder the triad is the table boad. It represent the physical database table, and decomposed in 3 MVC classes. this is called triad.