Local Line vs Chuo Line

I search for the route vi hyperdia. It refer to "local service for Chiba" what is the difference?

Searched which stns fr/to?

That section is one of double/parallel tracks.
http://livedoor.blogimg.jp/elle_riki_travel/imgs/f/e/fed1bf30.jpg
Orange(11) and Yellow(12) lines are so.
Stop stations are different.
http://www.jreast.co.jp/e/stations/e1647.html
http://www.jreast.co.jp/e/stations/e384.html
https://youtu.be/X-A847359vM
https://youtu.be/Yx8LkwTOS2A

You just don't know population also travelers for Tokyo.
https://en.wikipedia.org/wiki/Greater_Tokyo_Area
http://www.pasmo.co.jp/en/pdf/guide01.pdf
http://www.demap.info/tetsudonow/

Local "Service" and Local Line are two different things.

A Local service running along the Chuo Line is just that. Local normally means all stops pattern.

Others like Rapid or Limited Express for example have different stopping patterns.

When you get out of the main urban areas. You'll find most rail lines referred to as local lines, as they only have all stopping trains on them.

It's pretty well explained (with a graphic) on this page too:

http://www.japan-guide.com/e/e2372.html