...stretches the time axis.The timeline display can be increased or stretched and reduced or compressed, respectively.
For this purpose you can use one of the following three buttons in the timeline.
...stretches the time axis.
...restores the default setting.
...compresses the time axis.
Tip: Tool 
Pan also allows zooming of the timeline. Hold key P pressed and turn the mouse wheel.
Fast zooming via keys is also possible:
As an alternative, you can also press the keys + / - of the numeric keypad. The default display is resumed by pressing the X key (multiply).
You can change over between largest and smallest display by pressing the Ctrl key and clicking + or -.
In order to get an idea of the time dimensions, you should use normal view for your normal editing process.
The time display and the timeline resolution can be matched with the frame rate of the videos to be edited in order to simplify video cuts. See Changing time display and timeline resolution.
By increasing and reducing the track height, objects can be changed in their size, too. See Adjusting the track height.