Environment is the most important part of set in any framework.its indicates stores various contextual data used by the ORM method . For example you can see below code in you .py file .

@api.multi
... @api.returns('self')
... def demo_method(self):
...     return self
new_demo_model = env['a.model'].browse(1, 2, 3)
 new_style_model.some_method()
a.model(1, 2, 3)
 old_demo_model = pool['a.model']
old_demo_model.some_method(cr, uid, [1, 2, 3], context=context)
[1, 2, 3]
env = Environment(cr, uid, context) # cr, uid, context wrapped in env
demo = env[MODEL]                  # retrieve an instance of MODEL
recs = model.search(DOMAIN)         # search returns a recordset
for rec in recs:                    # iterate over the records
    print rec.name
recs.write(VALUES)  

Note with the help of this code you can set your environment easly.