Broad match keyword targeting is the default targeting method used in Adwords and if used incorrectly can generate thousands of irrelevant impressions and can use the adwords budget very quickly. There are few ways how to optimise the performance of broad match keyword targeting, and one of them is to add the plus (+) symbol in front of the words of broad match keyword. This type of keyword targeting is also known as “Broad Match Modifier“.
Basic broad match targeting will include any variation or synonyms compromasing chosen keyword term. Lets say you are an SEO company and providing SEO services, so you choose to target the broad match keyword search engine optimisation, however this keyword may generate a huge amount of impressions and send irrelevant traffic to your website, because it will trigger all different variations of that keyword such as people looking for search engine optimisation blogs, forums, turorial, ebooks, seminars etc. In order to narrow the search volumes you have to add modifier at the front of every keyword ie. +search +engine +optimisation . This keyword will trigger only then when all the words search and engine and optimisation will be used in the search query. Also, it is very highly recommended to use negative keywords in conjuction with broad match modifier in order to maximise the CTR and avoid irrelevant keywords.
Usage of broad match modifier
Correct: +search +engine +optimisation
Correct: +search +engine optimisation
Incorrect: + search + engine + optimisation
Incorrect: +search +engine -optimisation