Are all backlinks the same?

No. The most important characteristics of a backlink are quality and relevance. Quality refers to the credibility of the website linking to you. Government websites (ending in .edu) or well-known and trusted sites (like newspapers or popular industry resources) carry more weight than new, unknown websites. 

Relevance is also crucial. If you run a landscaping business, a backlink from Bunnings is worth more than a backlink from KFC. The more relevant the sites are that link to you, the better your backlinks are for your SEO.