Outlook tasks can have alot more properties attached to them and a lot more rich data in the description field than Google Tasks. GogTasks does the best out of this and synchronizes what it can, while making sure none of the data is lost in Outlook when synchronizing back.

Examples of rich data in description field:

Bullet lists (like this one)
Embedded images
Embedded documents
Link to mails

Examples of extra properties on Outlook tasks:

Start date
Priority
Completion percentage (as opposed to the boolean state)
Importance indicator

Below is an example of a synchronization process of a task with rich data from Outlook to Google and back to Outlook:

1. The task at Outlook initially

The task contains a link to an Outlook email and a bullet list, which are rich elements.

2. The task at Google after first synchronization

An alteration is now being made to the task - the name "Jim" is replaced with "Elizabeth" and we do another synchronization.

2. The task in Outlook after second synchronization

The conclusion is that the text of the description field can be freely edited at Google without interfering with the images and documents attached, but you will lose the rich formatting.