This means install the gem, but do not call require when you start Bundler. So you will need to manually call
require "whenever"
if you want to use the library.
If you were to do
gem "whenever", require: "whereever"
then bundler would download the gem named whenever, but would call
require "whereever"
This is often used if the name of library to require is different than the name of the gem.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…