regarding with radio buttons actions

i just want to ask...

the different terms ("names") of an action that will be implemented when defining an action for a radio button

example code:
ActionListener sliceActionListener = new ActionListener() {

another one:
ActionListener crustActionListener = new ActionListener() {

anothe one:
 ChangeListener changeListener = new ChangeListener() {


what is crust? in radioButton action? what kind of action is that? (english pls)
what is slice? in radioButton action? what kind of action is that? (english pls)

it it a good way of practicing my coding habit? when defining a term?

or is it still ok to define my own term... ?

for example my radioButton is just for selecting. is it fine to define it as 
selectionAction
?