AltaVista, owned by Yahoo (a company founded in 1994), was a very popular search engine in the early days of the internet, and its creators helped to make internet searches quick and easy. Then when Google was set up in the late 1990s Altavista was soon overtaken and by around 2002-3 many people were talking about 'googling' new information rather than looking it up. Other search engines were still in use but worldwide they were less popular than Google. AltaVista suffered particularly, and in 2011 Yahoo briefly shut it down. It was reopened in 2012, and you can still use it now and it still works - please click here and try it out.
As you can see, the new AltaVista page clearly indicates that it is part of the Yahoo brand. Whether it will have anything like its old success is hard to say, but as an old internet user I'm glad to see it back!