What is page authority and how does it differ from domain authority?

Page Authority (PA) and Domain Authority (DA) are metrics developed by Moz to predict how well a specific web page or entire domain is likely to rank in search engine results. Here's how they differ:

1. **Page Authority (PA)**:
   - **Definition**: Page Authority measures the predictive ranking strength of a single web page. It predicts how well a specific page is likely to rank on search engine result pages (SERPs) compared to other pages.
   - **Factors**: PA is influenced by factors such as the number and quality of backlinks pointing to the page, the relevance and authority of those linking domains, on-page SEO factors (like content quality and keyword optimization), and other MozRank and MozTrust scores.
   - **Use**: SEO professionals use Page Authority to assess the strength and potential ranking ability of individual pages on their website or competitors' pages.

2. **Domain Authority (DA)**:
   - **Definition**: Domain Authority measures the predictive ranking strength of an entire domain or subdomain. It indicates how well a website is likely to perform in search engine rankings compared to other websites.
   - **Factors**: DA considers similar factors as PA but applies them to the entire domain rather than a specific page. This includes the overall quality and quantity of the site's backlink profile, domain age, popularity, and other metrics related to MozRank and MozTrust.
   - **Use**: DA is used to evaluate the overall authority and SEO strength of a website. It helps SEO practitioners understand how competitive a website is in its niche or industry.

**Key Differences**:
- **Scope**: PA focuses on individual pages, while DA assesses entire domains.
- **Purpose**: PA helps evaluate the potential ranking of specific pages, while DA provides an overall picture of a website's authority.
- **Application**: PA is useful for optimizing specific pages for SEO, while DA is valuable for competitive analysis and benchmarking against other domains.

In practice, both Page Authority and Domain Authority are useful metrics for SEO professionals to understand and improve their site's ranking potential. They provide insights into the quality and strength of a website's pages and overall domain in relation to search engine rankings.