From BlenderWiki

The Window System

When you start Blender you should see this sequence of events:

• A console window appears (under Windows only!).
• Shortly after, the main user interface window will display the default Blender scene.
• You may see a splash screen announcing the Blender version: it usually disappears as soon as you move your mouse, so if you move the mouse at the startup too quickly, you may not notice the splash screen.

Every window you see can be further broken down into separate areas (see this page) – below we describe the default scene.

The default scene

The default Blender scene shows the screen you should get after starting Blender for the first time.

By default it is separated into three windows:

• The main menu at the top is the header part of the User Preferences window.
• A large 3D window (3D View window).
• The Buttons window (at the bottom).

As an introduction we will cover a few of the basic elements.

The main top menu

All windows in Blender have a header. See this page for an in-depth description about headers. This is the header for the User Preferences window, which is by default “hidden”. Its primary use is as main menu bar…

Check the image above for reference.

• Window Type: Allows you to change what kind of window it is. For example, if you want to see the Outliner window you would click and select it.
• Main Top Menu (User Preferences Menu): This is one of the greatest similarities between Blender UI and classical applications ones. This menu gathers some common, general commands, like file load/save, help, etc.
• Current Screen layout (default is Model): By default, Blender comes with several pre-configured Screens for you to choose from. If you need custom ones, you can create and name them.
• Current Scene: Having multiple scenes present allows you to break up your work into organized patterns.
• Resource Information: Gives you information about application and system resources. It tells you how much memory is being consumed based on the number of vertices, faces and objects in the selected scene. It is a nice visual check to see if you are pushing the limits of your machine.

3D Window View

Check the image above for reference.

• 3D Transform Manipulator: It is a visual aid in transforming objects. Objects can also be transformed (grabbed/moved, rotated, scaled…) using the keyboard shortcuts G, R, S. CtrlSpace will display the manipulator pop-up. The manipulator visibility can also be toggled by clicking the “hand” icon on the toolbar (header). The translation/rotation/scale manipulators can be displayed by clicking their respective icons, to the right of the “hand” button. ⇧ ShiftLMB -clicking an icon will add/remove each manipulator’s visibility.
• 3D Cursor: It is the materialization of a 3D location. It has many functions – for example, it represents where new objects appear when they are first created. It can also represent where the base (pivot point) of a rotation/scaling will take place.
  Here is the 3D Cursor isolated from the rest of the scene:
• Cube Mesh: By default, a new installation of Blender will always start with a cube mesh sitting in the center of the global 3D space. After a while, you will most likely want to change the “Default” settings. This is done by configuring Blender as you would want it on startup and then saving it as the “Default” using CtrlU (File » Save Default Settings).
• Light (of type Lamp): By default, a new installation of Blender will always start with a light source positioned somewhere close to the center of the global 3D space.
• Camera: By default, a new installation of Blender will always start with a camera positioned somewhere close to the center of the global 3D space and facing it.
• Currently selected object: This field shows the name of the currently selected object.

3D Window Header

This is the header for the 3D window. All windows in Blender have a header (and like in this case it may actually be a footer at the bottom of a window, but we’ll still call it “header” here anyway). See this page for an in-depth description about headers.

Check the image above for reference.

• Viewport shading: Blender renders the 3D window using OpenGL. You can select the type of interactive shading (called Draw Type in the Blender shading list) that takes place by clicking this button and selecting from a variety of shading styles. You can select from boxes all the way to complex textured shading. It is recommended that you have a powerful graphic card if you are going to use the textured style.
• Rotation/Scaling Pivot point: Allows you to select the center from where rotation/scaling will occur. For example, rotation could occur around the object’s local origin, or around the 3D cursor’s position, amongst many others.
• Layers: Make modeling and animating easier. Blender layers are provided to help organize your objects into functional groups. For example, one layer may contain a water object and another layer may contain trees, or one layer may contain cameras and lights. These buttons then control the visibility of each layer’s objects, making it easier to work on a subset of the objects in your scene.

Buttons Window Header

All windows in Blender have a header. See this page for an in-depth description about headers. This is the header for the Buttons window.

Check the image above for reference.

• Editing Panel Group: The bottom window displays panels and those panels are grouped. This row of buttons (called “context buttons”) allows you to select which group of panels (a.k.a. context) is shown. Some buttons will display additional buttons (called “sub-context buttons”) to the right for selection of sub-groups or groups within groups (a.k.a. sub-contexts).
• Current frame: Blender is a modeling and animation application. As such, you can animate things based on the concept of frames. This field shows what the current frame is.

Buttons Window View

Check the image above for reference.

• Panels: These help to group and organize related buttons and controls. Some panels are visible or invisible, e.g. depending on what type of object is selected. And several panels might be regrouped together, giving “super-panels” with tabs to access each “real” panel.