Content is really dependent on the keywords you focus on and that is why they always come together.
But content is more than just writing text around keywords, it needs to be updated on regular basis to make SEO-friendly features of your site work.
It comes in many forms, not just text but also videos, photos, blog articles, products for sale, reviews, offers, the list is endless...
In SEO terms, content can also be referred to as “On page elements” and it should include some or all of the following features: keywords; alt tags; anchor text; headers; title elements;
There are also Off-Page Elements that could include additional information like meta data .