delegate use in sencha touch 6

Good morning Folks!

If you have a sencha FieldSet and has many fields, you can delegate an event to his sons:

fieldset.on({
        change: 'ChangeFieldValue',
        delegate: 'field',
        scope: me
    });

Also, I haven't find good documentation about delegate events. If anybody know about it please let me know.

Working with:
Sencha 6.0.2.14

free knowledge.