The Proportional Editing tool is then Available in Editmode for all Object types. This tool works like a 'magnet', you select a few vertices and while editing (grab, rotate, scale) the surrounding vertices move proportinal with it. Use the NumPad-plus and NumPad-minus keys to adjust the area of influence, this can be done "live" while editing. Especially the proportional Editing while rotating gives many good effects, for example the helix from the image below is made with PET.
You also can change how the area of influence is shaped, there are two possibilities adjustable with the IconTogs right of the PET Icon. The Effects of these two possibilities you can see in the image below.