La Tomatina seems to be a fun event wherein participants of the event are given a chance to throw tomatoes at each other for a certain period of time. Throwing tomatoes does not mean that you are angry at another person; you are just doing this so that you can all become entertained.
There are some rules that should be followed like it is not allowed to use and throw hard objects as this may hurt other participants. People are not allowed to remove and throw their t-shirts during the event. The tomatoes should be a bit squashed before they can be thrown so that they will not hurt. People should keep a safe distance away from the lorries.