Under your name, on your LinkedIn profile, there's a small space to provide a brief statement about yourself.
I call it your tagline. Neal Schaffer calls it your Professional Headline. That's good too.
He says it's the most important part of your profile and I agree.
Let's say you're a recruiter. You run a search on Linkedin for electric motor designers in Cleveland. You get 50 results.
That's a lot of profiles to review and you don't want to read the details of every one. You want to open the page, look at the tagline and have it tell you if it's a good idea to read on.
If it says: Electric Motor Designer, you know you're on the right track.