There are 3 things to consider in your keyword research:
In terms of intent, think of these two keywords:
Here we have two keywords in the same niche but the level of intent is different. The first one is more research-based and you could find it in the higher parts of the funnel.
The second example is slightly higher intent because the person is searching for something specific.
In terms of volume, this is a relatively simple concept. Keyword search volume is just how many people are searching for your keywords. If this number is too low, you may struggle to get your ad in front of enough searches.
The final one is competition and this is where PPC tools like SEMRush will help you out. With these, as well as in Google’s Keyword Planner, you can see bid ranges, keyword difficulty (how hard it is to rank), traffic, etc.
Essentially, if a keyword is being bid on by many advertisers, it may be harder for you to get your ad shown, especially at a cost-effective level. It can also give you insight into landing page optimisation so that you can understand what keywords you should include, helping you rank higher.
Hope this helps!