String data type
A String is an ordered sequence of bytes, not a string literal. Think of strings as an indexed array of bytes.
This means that you can store arbitrary data in a string, such as a string literal, an integer, or a float. You can also serialize JSON to a string or binary format and then store it in a string.
You can SET and GET a string. A SET writes the string to the database and a GET returns the string. As with all data types, you access a string via its key.
You can APPEND to the end of a string and get the length of a string via STRLEN.
The fact that a string acts like an indexed array of bytes means that you can access substrings. SETRANGE allows you to overwrite a substring while GETRANGE allows you to query a substring.
The ability to append to a string combined with reading and writing substrings allows you to use a string for compact data storage.
Strings are often used for more than simple key/value storage. You can also use a string to store a serialized object or database row.
