The String Type values -regarding

I have questions
1

In this sentence

The String type is the set of all ordered sequences of zero or more 16-bit unsigned integer values (“elements”) up to a maximum length of 253 - 1 elements.
string-type

my question is if boolean type has values true & false. in what aspect, string type mentioning elements for values.
what is "set of all ordered sequences"? whether they are mentioning integers like this
->0123456789..... or else some other things. If i get full details for the quoted sentence with example it will be helpful.

2

For simplicity, in this context, you can think of a "16-bit unsigned integer value" as a character. So a String value is an ordered sequence of characters (from zero to 2^53-1 of them). The String type is the set of all possible String values.

3

Thankyou.