Question re. Bernt's agenda setup

[Manish <mailtomanish.sharma@gmail.com>]

Hello Bernt and others,

I was picking up tips from Bernt's awesome and famous document at
http://doc.norang.ca/org-mode.html.  In section 7.1, just between the
two screenshots, I came across following text:

,----[ excerpt from section 7.1 ]
| After selecting a project (with P on any task in the agenda) the block
| agenda changes to show the project and any subprojects in the Projects
| section. Tasks show project-related tasks that are hidden when not
| narrowed to a project.
`----

The feature/concept seems very useful to be able to zoom into a project
of interest but I could't figure out how =P= helps with this since it
seems to move to previous item while in the ageda view.

Can someone (or Bernt) using the setup point me to right direction
please?

Regards
--Manish