a itself (the pointer) is defined as a local variable (implicitly) using the auto storage class, so it's allocated on the stack (or whatever memory the implementation uses for stack-like allocation -- some machines, such as IBM mainframes and the first Crays, don't have a "stack" in the normal sense).
The string literal "tesaja" is allocated statically. Exactly where that will be depends on the implementation -- some put it with other data, and some put it in a read-only data segment. A few treat all data as read/write and all code as read-only. Since they want they string literal to be read-only, they put it in the code segment.
