ADEGBE DAVID - The webstorage plugin is the outdated version of the localstorage. Even if webstorage is replaced, it is still usable if you are not going to publish in chrome webstore. But if you are making a new game, make sure then to use localstorage since it is the lastest type of offline storage.
Localstorage is the same as webstorage, the difference is that the localstorage is more efficient since it only runs as a function or trigger when you call it. Webstorage was replaced since it was always checking the keys and values since it was running every tick. Both has the same use, that is to store offline keys and values for example key("HighScore") value(10)points. Hope that clarifies it.