Strokes are performed by moving a finger or stylus on the touchscreen. Gestures involve moving the device itself. Additionally, it is possible to use buttons, switches, or other controls based on the touch screen actions.
When using either strokes or gestures, they should be taught and indicated to the user. It should be clear to the user where on the screen strokes can be performed. Many users like to have more traditional interaction methods (like buttons and sliders) available in addition to strokes or gestures; this way, they are available as backup, if the right stroke or gesture is forgotten.
For instance, even if zoom functionality is provided using strokes, providing a slider pop-up in the toolbar can be useful.
Tip: With strokes and gestures or other complex controls, clear feedback is necessary. More abstract gestures require more straightforward feedback, in order for the user to acknowledge that the gesture is registered.