C basic

what is the difference between the following declarations in terms of memory and internal processing in c?

>>>> char='a'; Vs string="a";

How is the Vs type defined? In 23 years of professional C and C++ programming, I have never ever seen it until right now.

Techically, there is no difference. They are both errors. But answering the question:
char var = 'a'; defines a single character named var with the value of 'a'

string var="a"; defines a string variable (essentially a multi-character array) named var with the value of the single character 'a'.

More characters can be defined or added to a string. They cannot be added to a char since it defines only a single value.