The word "too" is an adverb that indicates excessiveness or addition. It is often used to express that something is more than what is desired or acceptable. For example, in the sentence "It is too hot outside," the speaker suggests that the temperature is uncomfortably high. Additionally, "too" can also mean "also" or "as well." In this context, it is used to add information. For instance, in the phrase "I want to go too," the speaker is expressing a desire to join someone else in an activity.