The Binary tab is useful for "peeking" inside some data formats that can't be displayed normally – such as "HDROP". It is also useful as an investigative tool, such as if you're wondering why you have an extra line-feed when copying from a certain application – this can show you, as you see all of the bytes in the data. You probably won't use this very often, but it is handy if you need it.
Note: This tab is disabled by default. Enable it in the "Editor" tab of the options dialog.