twitter would like to borrow money from you. they will pay a reduced interest rate on the loan. in exchange, you will get the option to convert your loan into shares of twitter at a designated, unchanging price--likely near the current stock price.
this is a great deal for twitter, as long as their stock price does not go up. in other words, twitter is calling the top of the market for its own shares -- to the tune of 1.3B.
bezos did this to great effect with amazon in the late 90s. he did in fact correctly predict a prolonged stagnation in share price.