2.4.1 The buttons 

In Blender, buttons are always activated with the LeftMouse. These are the button types: 

(but)  
This button activates a process, like 'delete of 'new'. They usually have a salmon color.  

(tog)  
This is a binary button: true or false. It defines options and settings.  

(radio)  
Buttons sometimes form a row, only one of the options can be active.  

(num)  
This button shows the value of a variable. These are the ways to use it: 
- LeftMouse click, hold and move the mouse. Moving left/down is for a lower value, up/right is a higher value. 
- while moving: press SHIFT for a finer control, press CTRL for steps. 
- LeftMouse click, hold and MiddleMouse click: the button becomes a text button. Type the desired value and press 'Enter'. Press ESC to restore the value.  
- Click/release at the left or right side of the button decreases/increments the value with a small amount.  

(numsli)  
Click at the slider, hold and move to change the value. The left part serves as a text button.  

(text)  
To enter text, click on this button. A text cursor appears at the indicated location. This button remains active until 'Enter' or LeftMouse has been pressed or when the mouse cursor leaves the Blender screen. 
Some tips: 
- ESC: restore original text or value. 
- Shift-Backspace to clear the contents. 
- Shift-ArrowLeft of Shift-ArrowRight to move the cursor to the start or end. 
 

(menu)  
This button pops up an overdraw menu. Hold and move the mouse to make a choice. Move the mouse too far, restores the original value. 

2.4.2 Header buttons 

(icon)  
Almost all header buttons have icons. It can be type 'but', 'tog' or 'row'.  

(iconrow)  
Indicated by small arrows at the sides, this is also a row button. Click/release at the left or right side of button to change the value. 
Click hold and move the mouse a faster way to select an option.  

  
You find this combination in headers of Buttons, Curve, Image and Info windows. It visualizes (the link to) a certain data block. In this case, a Material. 
- The leftmost menu button can be used to browse another Material, or to add a new one. 
- The text button displays the name. Data blocks in Blender always have a unique name. 
- If there's a button with a number, it represents the number of 'users' of this data block. Press this button to copy this block, make it "single user". 
- A button with an 'X' allows the user to break the link. The data block is still available (with the menu button). There are two exceptions: Scenes and Screens are deleted right away. 
- A button with an auto icon indicates an automatic name function. 

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