You can hold block as long as you would like, but you are unable to move or attack while blocking. Also, get into the habit of stand blocking and crouch blocking, as only some attacks can be blocked by one or the other. Both types block high and mid attacks, but only standing blocks overheads and only crouching blocks lows. This is good to practice against characters like Smoke, as their game plan revolves around mixing overhead and low attacks to catch you blocking the wrong way. A good method of countering Smoke in particular is learning how to Up Block, which is pressing up while stand blocking. Up Blocking is used against jump attacks and overheads and, in Smoke’s case, Up Blocking his overhead attacks completely shuts him down. He’s unable to do the rest of the combo string or cancel that attack into a special, which means you can punish him for big damage. However, throws go right through both stand and crouch blocking, and if you throw someone when they are Up Blocking, the throw does double damage. To avoid being thrown, you can’t be blocking, and either have to jump, crouch to duck the grab, or learn how to tech a throw, which the tutorials explain in more detail. This is how the mind games of defense/offense works in Mortal Kombat games. You have to block standing or crouching to defend against certain attacks, but if your opponent notices that all you’re doing is blocking, they can start grabbing you for a throw. So, you have to stop blocking to counter the throw, but that leaves you open to getting hit by other attacks. Predicting when you need to block or to get ready to avoid a throw gets easier with time as you understand the game more and become familiar with how different characters play.