To explain each of these:

Navigational Queries

These are what you would search when trying to find a particular website. For example, you could enter “facebook” into Google’s search box to find the facebook instead of entering http://www.facebook.com into your browser’s address bar .

Informational Search Queries

These are “research queries”. As the name suggests, these are queries which you would type when looking for information about a product, service or subject matter without any bias toward a particular website. For example, the search “what is the answer to life the universe and everything” is as much a search for information as just searching the phrase “dirt bike”. The first query being specific but posed in the form of a question and the latter being very broad and allowing ambiguity.

Transactional Search Queries

These would be what you would search with the intent to actually make a purchase. A good example would be “buy dirt bike” instead of “dirt bike”, which suggests an intent to make a purchase and suggests that you are actually looking to make a purchase online or offline.

When thinking about keywords which will bring you ROI (Return on Investment); transaction searches are clearly the way to go as navigational and informational search queries are extremely hard to monetise. SEM (Search Engine Marketing) and SEO (Search Engine Optimisation) campaigns that capitolise on this knowledge have a greater likelihood of achieving a higher ROI, effecient PPC (Pay per Click) tactics and a greater insight into your ideal customer’s purchase behaviour.