myString  = "This is a string".
That (myString) is a C string. The '\0' at the end (not shown) is there to show the end of the string, since two strings might be contiguous in memory and appear to be one long string without the terminator. I hope this helps, though there seems to be little point in describing it in some way other than an array of characters terminated by zero. That's a perfectly good definition.
The string class available in C++ is another thing entirely.