The two tools from left to right are:
* Draw an AOI by clicking each point and double clicking to complete
* Draw an AOI by freehand sketch - hold down the mouse and sketch
If the dataset you are viewing/downloading is a public dataset then you can draw your AOI anywhere you like.
If you are a registered user viewing/downloading a restricted dataset, then any AOI you upload, or draw, will be clipped (restricted) to your default AOI as shown below as that is the area you have been authorised to download restricted data for.