Object numbers behave the same way numbers do, there is a max object number that can be represented, and a minimum. Object numbers represent a named object in the MOO database. Object numbers can't have math operations performed on them. Object numbers are not numbers, they are a constistant way to refer to certain sections of the database. Strings Strings are MOO values that can contain any printable character.
Strings can be of any length.
There are a number of builtin functions that handle strings. Errors Errors are a MOO type that are used when an error occurs. Errors have both a short name, which is the actual error value, and a string value, which is a more descriptive form of the error. Lists Lists are like arrays in other languages. Any MOO type can be in a list, even other lists.