MobileOrg allows you to capture notes whether you are online or off. Notes are uploaded to the server during the next sync.
To capture a new note, click on the Capture icon in the application toolbar, then click the + icon in the navigation toolbar. Enter in your note, then click Done.

The number of notes waiting to be synced appears as an indicator count by the Capture toolbar icon. After you sync, this count disappears to let you know you have no pending notes.
Notes are appended to the end of the mobileorg.org file on your WebDAV server. If this file does not exist when you try to sync, MobileOrg will attempt to create it.
It is generally NOT recommended to reference mobileorg.org as a link from your index.org file.
When you get back to your desktop computer, you can refile your captured notes into your primary Org-mode files by following these steps:
M-x org-mobile-pull RETfrom-mobile.org in your default org directory (variable org-directory). You may specify a different file and location by explicitly setting the variable org-mobile-inbox-for-pull.from-mobile.org buffer, and using C-c C-worg-mobile-pull function. Those changes will only appear in from-mobile.org if they could not be applied (e.g., if the target Org-file changed so much that the context can no longer be located).If you are not using the Org-mode integration, you can disregard these steps and manage the mobileorg.org file yourself using whatever means you choose.