SEO, an acronym of Search Engine Optimisation, is a technique used to improve ranking of a website in Google or in other search engines. Basically, SEO content writing is to serve the very core objective of SEO as defined. Means, SEO content should be seo specific, that is, to write contents according to keywords specified. However, cautious should be maintained while including keywords. You cannot/should not stuff SEO content with keywords.
How to write SEO content?
well, if you CAN write, then you can write contents related to SEO. This is not a rocket science at all. it's as simple to understand (if you know write well) as reading A,B,C of English alphabet.
YES, there are specif keywords to be used in SEO content writing.
BUT, keywords can be prioritized according to their relevance of inclusion in contents. So, basically there are two types of keywords - PRIORITIZED and SECONDARY keyword/s.
PRIORITIZED keyword/s is/are usually placed in title and the first para of content, while the SECONDARY ones can be placed anywhere in the content, one or two times (depending on the length of content or as instructed).