Usually, when we are looking to promote our keywords and phrases, we choose them based on what we think the user will be searching for. With the Google Suggest tool (edit: now known as Autocomplete), searches are starting to appear differently to how they used to.
What is Google Suggest?
Google Suggest is a method that helps users by suggesting words and phrases that they may be looking for as they type. For example, if I start to type "Web" into my Google homepage, the search box responds with the following helpful suggestions of what I may be looking for:
This can be very helpful in certain situations, but this does perhaps alter what phrases actually get searched for. If I expand my earlier search to look for "Web Design Introduction", as soon as I get to the point of typing the "in" from "introduction", I get presented with a list that includes the phrase "web design in a nutshell":
That's not a phrase I would have initially chose to search for, but it's certainly a phrase that could describe what a user was looking so they may just click that suggestion and perform that search.
What implications do these searches have?
Well, the first thing that comes to mind is "have I optimised my site for this type of search"? Probably not, I guess but it might just be one of those phrases that doesn't have as much competition so may be easier to rank for. I'd suggest that you try doing the type of searches you have optimised for and simply having a look through the list of suggestions to see what else you should look at incorporating into your website text.
Secondly, as it's quite easy to just click on a suggestion, you'll find that that users actually end up searching using phrases that are perhaps longer and contain more words then they may necessarily have searched for without the suggestions. This is another tool that you can use to your advantage as if you match on an exact longer phrase, you'll have more chance of appearing higher in the rankings. Longer search phrases are also becoming more popular, so this could be a very useful way of getting better results for your site(s).