If you are a freelance writer or copywriter, you probably have a fairly broad skill set.
If I asked you what you did, you might say one of the following:
“I’m an online sales copywriter.”
“I’m an online content writer.”
“I’m a social media writer and marketer.”
There is nothing wrong with those descriptions, in so far as they describe a general area of expertise. Behind that claim you could have a ton of training and professional experience.
The limitation of describing your value in these broad terms is that you will find yourself lumped together with thousands of other people who describe themselves in exactly the same way.
For example you could be a terrific online copywriter. But when someone hears you describe yourself with those words, they might think, “Yep, you and a thousands of other people like you.”