Google 4 Manual Book page 226

Configure auto-sync for all apps
To control Anto­sync for all apps that use it,
open Settings > Data usage > Menu and
check or uncheck Auto-sync data.
If you turn off Auto­sync, you need to sync
manually to collect messages, email, and
other recent information, and won't receive
notifications when updates occur. For exam­
ple, changes that you make in your People
app are automatically made to your Google
contacts on the web.
If this option is not checked, you may be able
to use an app's tools to sync data manually.
You can also sync manually to collect mes­
sages, email, and other recent information.
Leaving Auto­sync off can help extend your
battery life, but will prevent you from receiv­
ing notifications when updates occur.
PERSONAL, SETTINGS 217