This answer varies based on the external websites that send traffic to your website. Let's take a deeper look - A referral can be defined as any traffic that comes to your site from a link on another site. This can include things such as a third-party website or a recent blog that mentions your website and links to you. The referral source can be useful to determine which third-party partnerships are delivering measurable results to the business (e.g. brand collaborations) and help to highlight those that are not (spam traffic). Adding referral exclusions can help you to eliminate spam traffic from your reports, and will help you to get a better understanding of how your referral traffic performs in comparison with other traffic sources (Paid Ads, Organic Traffic etc.).
An example of a good referral would be a high-quality website that regularly leverages content from your site for their blog content. However, you will also find a number of poor referral examples from low-quality websites. Good Referral Example: HubSpot - Reputable website that regularly references your site in their blog posts. Poor Referral Example: Xxyx123.com - Poor quality site which is sending traffic toward your domain. Note for any planned traffic (for example paid advertising or affiliate marketing) we recommend you to request that utms are applied so you can recognise that traffic and associate to your marketing efforts.