Both https://duckduckgo.com and https://start.duckduckgo.com present as the first page of the search engine. I configure my browser to pass search queries to either of them.
I learnt about the start.
domain when I stepped through a tutorial/infobox on the regular domain that suggested something like "never see this again".
What is the difference if I use one domain rather than the other? (I'd prefer official documentation that clarifies the goal rather than (just) the implementation.)