The 36-year-old striker revealed that the rich past and scale of the Ibrox club were key attractions in his decision to join, in addition to the chance to work for ex-England team-mate Steven Gerrard.
"I wanted to come here for obvious reasons; I've always known it's a massive football club," said Defoe, who underwent his first training session in Tenerife on Tuesday.
"The history of the club... as players those are the sorts of clubs you want to play for and do well at. You want to be part of the history if you can.
"It was an easy decision to be honest. If you love your football like me and you get an opportunity like this it's hard to turn it down.
"I've been in the Premier League for so long and it's always nice to have a different challenge.
"Sometimes you can - not get comfortable - but you are in your comfort zone there and sometimes it's nice to get away from that and just try and find that fire again, set targets and have a different challenge.
"Winning trophies was another draw, especially how well the lads have done since Stevie has been in.
"Being a part of the history and doing something special here, that would be amazing to be involved in."