jq is great for shell scripts. Say your script hits an API that returns JSON, and you want to retrieve a single field. This can be difficult to do correctly with grep or other text matching tools, but is trivial with jq. You just pipe it in like "curl XYZ | jq '.path.to.your.data'"

I imagine this is how it's used 90% of the time, but can do lots more advanced stuff as described in the article.