What is the deference of configuration >> Settings >> General>> Force SSL for all site pages and configuration>>Store>>SSL Enabled

By default installation , configuration >> Settings >> General>> Force SSL for all site pages is checked

How about I have two store , one have SSL Cert. so check SSL Enabled, and other one have no SSL Cert. so unchecked.

Hello,

The setting in your store (Administration -> Configuration -> Store -> SSL Enabled) enables the SSL on your store. However, if you don't have the Force SSL for all site pages (Administration -> Configuration -> Settings -> General Settings) the only pages on your store that will open using the Secure Url are like the Cart page and Login/Register pages.
If you check the Force SSL setting, all of your pages will be forced to be opened with the Secure URL.

Hope that helps!

Regards,
Anton