The game-theoretic framework, introduced by Vovk and myself in 2001 (www.probabilityandfinance.com), uses game theory instead of measure theory as a mathematical framework for probability. Classical theorems are proven by betting strategies that multiply a player's stake by a large factor if the theorem's prediction fails. In this talk, I will discuss the basic idea of game-theoretic probability and two important applications: (1) defensive forecasting, (2) the game-theoretic interpretation of Bayesian and Dempster-Shafer inference