An action that can be called multiple times by the test in 
which it was created.(local test) as well as by other tests.

if  we eant to use the 'call to existing action' option, we 
have to make an action as reusable action. 
for that we have to go for action properties and click the 
check button.

let action1 is a reusable action then we call it to any 
other action. If  we change the script in action1 it is 
affects in all actions in which we called action1.
by 
vijay(SDG)