Permalinks are addresses of a particular webpage we type or click to visit in the browser. Search engines also use these Permalinks of WordPress websites to show in search results.
Changing the Permalink structure in WordPress site can be done with just 2 clicks. Just go to dashboard and click settings, then click permalinks and opt the desired structure.
But there is something more to know about permalinks.
We should aware of these following 4 points when we change the permalinks structure from defaults.
1) Stick to one permalink structure:
If we keep changing the permalinks structure in WordPress site, search results may lead to 404 page. Search engines will take time to crawl the new Permalink structure. Not only search results, internal links of the site also break and lead to 404 page. When website grows with more number of pages, it will be very difficult to handle internal broken links. So sticking to one Permalink structure is very important.
2) 404 errors handling with permalinks:
If you are using custom Permalink structure and if your web pages are redirected to 404 error pages even if the pages exists, try changing the permalinks structure to defaults. later you can change to previous settings. This helped me in some of cases particularly when moving the site from Localhost to online server or restoring the backup of WordPress site or moving the site from one hosting service provider to another service provider etc.
3) Change permalinks only after final review of site:
When we are creating a new website, It is better not to change the permalinks structure till final release. Because sometimes we may change the title of page (for better SEO or for any other purpose) even after creating and linking that page in content of several other pages. In such situations, it saves a lot of time in resetting broken links.
4) Make sure Permalinks are SEO friendly:
It is better to change the default permalink structure as search engine friendly. The best one is website name/page title/. Having a keyword in URL of a page/post is one of the major SEO positive factors. This helps search engines for better crawling. This change also helps the website visitor to understand what information it talking about simply by reading url of the page.
We can learn more about Permalinks at WordPress codex.