Towers

Towers are the main defense for your base. The towers that are closer to the nexus are the strongest towers whilst the outer towers are the weakest. If you played the tutorial you should know that minions are your best friend to taking down towers because they soak up all the damage. Towers do more damage with every consecutive attack. If you attack an enemy champion under the tower, it will target you first. Towers reveal all invisible targets. Also that destroying an enemy tower gives gold to everyone on your team. Apart from the towers in the bases, towers do not regenerate health, so if you just go for a little damage now and again it will be effective. But the towers in the enemy base are best to take down in one go, because if you get it down to nearly no health and have to run away, it can come back to full over time.

Not Targeted

Targeted

Tower diving is where you go under the tower to go for kills and or take the tower. Tower diving is best with teammates and to coordinate who will take the tower hits. For example, if the enemy bot lane is low and your jungler is ready to jump in. The most tanky teammate should go in first to take the damage from the tower and let the other two fight. These are done best when you are talking to people through Skype or Teamspeak. Other times you would dive a tower if you have a lot of health or armor and the enemy are really low and you know you can get the kill. The main thing to this is just knowing how much damage you can take and knowing how quickly you can go in and get out. Tower diving just takes a lot of practice like everything else in the game.