Who is Ken Jennings? Former Jeopardy! champion announced as first guest host of show

Jeopardy! announced Monday it will continue with a string of guest hosts following the death of beloved host Alex Trebek, and first on the list is Ken Jennings.
Jennings holds the record for consecutive games won at 74.            
Other guest hosts have not yet been announced.            
Episodes hosted by Jennings will begin taping at the end of the month and will air in January.
Trebek had hosted the show since 1984. He was diagnosed with stage four pancreatic cancer in 2019 and died earlier this month at the age of 80.