Scripting languages are Programming languages that use simple syntax (something similar to human language syntax)!
Programming languages syntax are normally similar to machine code!
So, since "AutoIt" is a programming language with simple syntax, thus it is considered a scripting language!
The problem with "AutoIt" is that it is a 100% interpreted Language, thus, it is a slow language too!
Why?
Because "AutoIt" does not convert its script file to "machine" code in order to the "cpu" understand it, so, the "cpu" will constantly need an "AutoIt" interpreter to translate the script, making all the process to slow!
loop, 1.000.000
var = var + a_index
The "AutoIt" interpreter must translate "var = var + a_index" to the "cpu" 1 million times! (the translation process is really slow!)
In the other hand, in compiled languages, all the script is converted to machine code, so, the "cpu" does not need an "interpreter" to execute the code, so no translation is required! (the loop above could be 1 million time faster in a compiled language than in an interpreted language!)