These new features allow you to re-rank your search results according to how you see fit. By hitting the promote button on a search result that sites will now be featured at the top of the search results whenever you type in that particular search result. You can also remove particular search results all together from the list so that next time you search the same keywords that result will not pop up.
There is also a comment feature that allows you to make quick notes about a result so that next time you search the same keywords you can see what you had to say about each of the sites.
SearchWiki is only available when you are signed in on your gmail account. So if you would like to remove search wiki you are going to have to sign out of your gmail account. Google has also posted a video explaining Search Wiki in further detail.