If you press the blue button and then select software updates you will see a list of available updates. This is an all or nothing list, you can't select the odd one or two. When you press the green button it will start to install them all. Once finished you will be prompted to restart your box. This is a full box restart.
99 times out of 100 everything is fine. A general rule of thumb is if you see the mention of Kernal in the update list, don't do the updates as these can cause your box to not boot and requires flashing.
The software updates you see are normally standard parts of openATV but from time to time, I will update some of the WooshBuild side of things such as WB Config, the picons etc so it is worth checking from time to time. I do tend to post when there is something I have updated though.