jinja2 is very useful

Hi everyone !

I have Question :

Sure I’m new in this community …

why we are using jinja2 in our playbooks ?
what can jinja2_extensions do in our ansible.cfg ?

e.g.

> [defaults]

jinja2_extensions=jinja2.ext.do

I can’t found an answer in officiel Doc : [http://docs.ansible.com/ansible/intro_configuration.html#jinja2-extensions] !!

tnx!