What are differences between Ext.create() and Ext.define()

Hi friends,

I have been learning SenCha Touch for awhile and still feel confused when trying to create a store.

In the SenCha Documentation, it says to use Ext.create() [Example]

I tried and it simply doesn't work.

For the rest of others, I always see people use Ext.define() to create a store and it works.

Now, my question is:

what are the differences between them and when and how to use either one of them?

Thanks a lot my friends.