OK say there is a blog.. and most of the blog is based on the subject of CHEESE.. and my site is based on BASEBALL.. if the cheese site does a post about baseball and then puts my link on this post only, will it be classed as a relevant backlink? So basically is relevance calculated via the WHOLE SITE or just by the SINGLE PAGE it's on ??
you will get some relevancy since the post where your link is on related to your niche and every blog has permalink so the page your link/article will be on is related. but it would be more related if the entire site was related to your niche.
Relevancy is a bit wide in SEO. Similar posts, topic, niche, field/category or theme can be considered relevant
I think both will influence in the relevance, first if in the URL its the word baseball it will be more relevant and then If the whole site is about baseball then you will benefit from it 100%
If the site you were posting your blog on was related to baseball that would be considered a relevant link.