There are 3 types of filters in Keyword Chef:
Keyword Filters are helpful when you want to filter by specific words in your report. This is helpful for ignoring keywords you don't want to see or for finding keywords around a particular topic (clusters).
Clicking the word will add that word as a "positive" keyword, where clicking it again will add it as a "negative" keyword. Clicking it a 3rd time will reset the filter.
You can also add your own word by clicking the plus sign.
The volume and SERP filter are together in the same section and are able to work together.
Adding a min or max search volume will filter the report for keywords with an avg volume within that range.
Adding a min or max SERP Score will filter the report for keywords with a SERP Score within that range.