Niiter itself is an aberivation or is short for “No filter Twitter”. It functions as an alternative frontend for popular social network. It also offers nitter viewing of tweets for users who are not signed up to twitter, unlike twitter which makes you sign up if you want to look around.
Nitter also markets itself as more what is nitter secure for users, than connecting directly via twitter.
Like Nitter for Twitter, there are also alternative front ends for some other social networks, like Teddit for Reddit, Piped for YouTube, etc.