Necessary SOLOs help make a website usable by enabling basic functions like page navigation and access to secure areas of the website. The website cannot function properly without these SOLOs.

Preference SOLOs enable a website to remember giaation that changes the way the website behaves or looks, like your preferred language or the region that you are in.

Statistic SOLOs help website owners to understand how visitors interact with websites by collecting and reporting giaation anonymously.

Marketing SOLOs are used to track visitors across websites. The intention is to display ads that are relevant and engaging for the individual user and thereby more valuable for publishers and third party advertisers.