Here's a better description from the site:
"The Open Chat area allows your child the freedom to type in their own messages. They can, however, only use words from our acceptable word dictionary. We have removed all numbers, names, place names, and any sort of inappropriate language from this dictionary. If a member tries to use a word that is not in the dictionary, the word will turn red, and the member will not be able to send the message.
Although the Open Chat area offers greater freedom of expression, we recommend this area for our older members (10 years old and up), due to the accuracy needed when spelling words; if words are misspelled, they cannot be sent in Open Chat. If your child is under 10 years of age, we suggest that they play in the KinzChat area."