You can now enable and disable the tool with just one click, set your Maximum Expenditure (the percentage of your budget to be spent on Related keywords), and aim the tool to find related keywords likely to bring more conversions.
The tool works by finding phrases similar in meaning to your keywords. The more you are willing to spend (the higher the percentage you set), the more relevant keywords the tool will find (including ones farther from the original) and the more impressions your ads will have. Likewise, setting a lower percentage will limit the range of keywords that trigger your ads.
You might also notice changes in the “Search queries” and “Report master” reports. The statistics now feature a new “Match type” column showing the synonym or related keyword that triggered the impression. By checking the original keyword linked to the impression, you can decide whether negative keywords are needed to prevent unwanted impressions, or if it’s better to delete the original keyword altogether.