In SEO, content refers to any type of meaningful piece of information displayed on your website. This can either be a copy, images, videos, infographics, etc. High-quality content is one of the main factors that will positively impact your ranking. To evaluate the quality, search engines look at specific criteria.
To be well-ranked, your content has to be:
1. informative and useful to the reader
2. unique (which means that duplicating text from another site is a no-no)
3. fresh (that is to say new, or regularly updated)