When view Ideas that other people have added, you can show your appreciation/support using the button. This will give the Idea more visability and any topics that are discussed within the Idea will be more prominent in the Trending Topics area.

You can see who else has appreciated an Idea by selecting the number next to teh appreciate button. It is not possible to appreciate your own Ideas, well.. not using innoloop, you are more than welcome to appreciate your own Ideas in private.
Using the button you can view or add Comments to an Idea. This is a really useful way to ask questions or expand upon an Idea that has been added by someone else.

When you add a Comment to an Idea, the person who added the Idea will be notified so that they can respond to you and carry on the conversation.