Dynamically update web content

Hi,
Could you give me some hints on the ways of reloading or updating one
web page from another web page?
For example, I have a main page is loaded contains some infomation, in
front of it, another small page is launched from a link of that main
page, the user will use this small page to edit some info passed from
main page, after finish editing, how can I dynamically reload and
update the main page from this small page?

Thank you.