Sometimes referred to as an inbound link, a backlink is simply any linked anchor text or image that directs users to another external website. Any strong off-page SEO or inbound marketing strategy is based on acquiring quality backlinks because they’re the pieces that make your site respectable. Generally, a site with a high level of authority will have a better PageRank score—these are typically popular sites like cnn.com, espn.com, or reddit.com—which means they’re like the Holy Grail of backlinks. So, too, are authoritative sites that are within your niche or a similar vertical.
But be wary of imitators lest you want to become like that dude from Indiana Jones who chose the wrong chalice.
How can you avoid “choosing poorly”? You should be (or have hired) a highly functioning Interneteer—ooh, a new term!—who can see the forest from the trees and smell a con before it walks in the room. You might be on the right path toward the Fountain of Youth if you can spot the difference between the low-ranking joeschmo.com site and the buildyourseofast1234.xyz site; even if joeschmo.com needs some webdev and website optimization work, it could still be a good source for an inbound link to your site, while the latter is likely a public backlink exchange site (aka. a big black-hat SEO no-no).
Being able to understand the differences between the two sites is but a small fraction of what it takes to be a backlink pro. Here are a few other creative ideas you can try out if you need a better balance of SERP and off-page/inbound traffic.