Keywords are what people will be typing to find you on the net.
There are plenty of free resources which will help you research possibilities:
One of the best articles on Keyword research can be found here through Moz.
I will be the first to hold my hand up and say that I leave all the keyword searching for SEO to the professionals as it’s a huge subject to get your head around however you can get free trials at Semrush or KWFinder
I personally use KWFinder as I found it to be easy to use and as much as I would have liked to use Moz I didn’t feel I would utilise their full offerings just yet to warrant the outlay.