This is perhaps the simplest method of link building. All you need to do is find a website that will allow you to post a link to your own page. Examples of such sites are:
- Social media profiles
- Forums, Q&A sites, and other similar web pages
- Job board websites
- Comment sections (e.g. on blog posts, Facebook threads, etc.)
Because it's so easy to post links in this manner, hyperlinks featured on these types of sites are not ranked very highly by search engine algorithms. Sure, it's a place to get started, especially if your business is new on the scene. But you should quickly look into other link building options.
That being said, don't completely dismiss adding links to other sites. Even if this method won't improve your search engine performance much, you might still attract customers using this method.