Web positioning happens when a website appears on the search page of Google or any other search engine index. A website main address should always position in the first places on the first page of the search results, when the SEO is correctly done, and when the search is done by using the domain name. However if the domain name is a common word or phrase, others websites may appear first. Also on the search page, there are some spaces reserved by Google Ads (on the head and footer of the search pages). If the domain name includes a very competitive word (keyword) the website may lose some places against those keywords.
When we talk about web positioning usually we may talk about URL positioning because every page of your website position differently depending on several factors.
While SEO implies web positioning, factors like Content, website structure, website load speed, and others are needed as well. Web positioning for other pages is the main goal of the SEO / SEM strategies.