Links are basically votes of trust for search engines. While a high-quality link counts as a high number of votes, a lower quality link will conversely count for a significantly lower number of votes. The basic characteristics of a high-quality link are the following:
- Trusted Source- A high-quality link will almost always come from a high ranking and trusted source.
- Hard to Get- It is a proven fact that high-quality links are significantly harder to get than low-quality
- Aged- Conventionally, links from older sources are trusted more than links from fresh sources.
- Co-citation- Certain pages which link to websites from the same category as yours and also link to your website make it more convenient for search engines to grasp the nature of your webpage.
Related- Generally links from related sources are given more importance than links from completely unrelated sources.