Writeability

To is a preposition (acts as a link or introduction to nouns, pronouns and phrases) that begins a prepositional phrase or an infinitive (to + verb =  infinitive).

Example: We went to the park. (preposition)  We like to watch cooking shows. (infinitive)

Too is an adverb meaning "also" or "excessively."

Example: I like chocolate, too. ("also")  She tans too much. ("excessively")