That it's an interesting feature of the views inheritance that I like to call it view inheritance by prototype because it's like the model inheritance by prototype where you create a copy of a model using this syntanx:

from openerp import models

class model_class_name(models.Model)
    _name = 'model.name'
    _inherit = 'new.model.name'
    ...
    ...

Defining the view like using the mode primary is the same as the model example exposed and you will end with a new view that inherit from the inherit_id view reference. That view field is only used in conjunction with the inherit_id field. By default have the value extension that it's the most used and known use.

Let's put an example assuming that you need two views of the model res.partner with different changes in how they fields will be displayed or whatever you need, could be that you don't want to use groups or invisible in all the fields that you need to add or modify in boths of the views or their position varies

<record model="ir.ui.view" id="partner_base_view">
    <field name="name">Client</field>
    <field name="model">res.partner</field>
    <field name="priority">1</field>
    <field name="arch" type="xml">
        <form string="Patient">
            <sheet>
                <field name="image" widget='image' class="oe_left oe_avatar" options='{"preview_image": "image_medium", "size": [90, 90]}'/>
                <div class="oe_left">
                    <label class="oe_edit_only" for="name" string="Name" colspan="4"/>
                    <div class="oe_inline">
                        <h2>
                            <field name="title" domain="[('domain', '=', 'contact')]" options='{"no_open": True}' placeholder="Title" nolabel="1" colspan="1"/>
                            <field name="name" default_focus="1" placeholder="Name" nolabel="1" colspan="5"/>
                            <field name="lastname" placeholder="Last Name" required="1" nolabel="1" colspan="6"/>
                        </h2>
                    </div>
                    <field name="category_id" widget="many2many_tags" placeholder="Tags..." colspan="6"/>
                </div>
                <div class="oe_right oe_button_box solt_oe_button_box" name="buttons">
                    <button class="oe_inline oe_stat_button" style="width: 250px !important;" type="action" name="322" icon="fa-phone" context="{'search_default_partner_id': partner_id, 'default_duration': 1.0}">
                        <field string="Calls" name="phonecall_count" widget="statinfo"/>
                    </button>
                </div>
                <div class="oe_clear"/>
                <notebook>
                    <page string="Personal Information">
                        <group>
                            <field name="marital_status"/>
                            <field name="religion"/>
                            <field name="ethnic_group"/>
                        </group>
                        <label for="comments"/>
                        <field name="comments" placeholder="Comments"/>
                    </page>
                </notebook>
            </sheet>
            <div name="message" class="oe_chatter">
                <field name="message_follower_ids" widget="mail_followers" />
                <field name="message_ids" widget="mail_thread" />
            </div>
        </form>
    </field>
</record>
<record model="ir.ui.view" id="partner_primary_mode_view">
    <field name="name">Client Extended</field>
    <field name="model">res.partner</field>
    <field name="priority">8</field>
    <field name="inherit_id" ref="partner_base_view"/>
    <field name="mode">primary</field>
    <field name="arch" type="xml">
        <xpath expr="//form/sheet/notebook" position="inside">
            <page string="Extra Info">
                <field name="extra_info"/>
            </page>
        </xpath>
    </field>
</record>