The least “advanced” of the 3 types which also applies to variations of the keywords chosen. If you choose, for example, the keywords:
download music videos
Your ad would also be shown for:
music download videos
videos music download
download videos music
In some cases this may not be in an issue but in others, when re-arranged, can mean something completely different to what a person is searching for and therefore become untargeted.
More targeted as it pinpoints the exact phrase, in that if you choose
“wii games online”
As you were in the business of selling console games online, it would also trigger:
buy wii games online
order wii games online
purchase wii games online
You do though run the risk of targeting unwanted terms such as
free wii games online
download wii games online
In this instance you would use the negative keywords feature and flag “free” and “download” so as not to appear for these terms.
The most targeted match where you set the exact keywords to trigger your ad. These tend to be more longtail and will generally have a better ROI. So returning to the first example, if you chose:[download music videos]
Then only when that phrase is entered will your ad appear.
Generally I’d recommend always starting on “exact” with various keyword combinations, in particular the high volume keywords. In some cases, such as “buy football boots manchester”, you could probably just as easy start off on phrase match due to it’s lower volume and fact it includes the word “buy” but always be sure to keep a check of what traffic you get on your phrase matches to look out for any words you should be adding as negative keywords. Once you have the majority if your keywords covered by exact and phrase, use broad to cover the lower volume variations.
The key though is to continually check your logs and use these to develop other keyword phrases as well as a negative keyword list.