Use DynamicModule to localize variables and prevent conflicts with their global counterparts:

Local variables are unique to the generated output:

Assign initial values to local variables, just like Module:

Define a function as a local variable:

Use DynamicModule to save the displayed state across different Wolfram System sessions:

Module only gives unique states in the current Wolfram System session:

Use Initialization to evaluate expressions before displaying the contents:

Initialization is evaluated after the local variable assignments:

Set the base style:

Specify expressions to be evaluated when output is no longer displayed:

Function definitions of local symbols are automatically inserted into DynamicModuleValues:

By default, certain system-internal contexts are not saved in the initialization option:

Use ExcludedContexts{} to save definitions of all non-protected symbols:

Create a dialog box with a DynamicModule that inherits variables from a parent DynamicModule:

By default, external definitions are lost between kernel sessions:

Use Initialization to save evaluations necessary for the content:

Local variables can also be initialized:

The initialization only runs if the output is displayed:

The first DynamicModule was suppressed by the semicolon, so it never ran its assignment:

Limit recursive inclusion of symbol definitions to the contexts "c1`" and "c2`" only:

By default, external definitions are lost between kernel sessions:

By setting SaveDefinitions to True, the external definitions are saved with the output:

By default, the initializations are evaluated before the output is displayed (synchronously):

Force the output to display while the initializations are evaluated asynchronously:

Create an interface that responds to the Undo menu command:

Specify symbols whose state should not be saved:

Evaluate the following and move the two sliders, then click Close:

Evaluate the following and note that the second slider does not remember its previous state: