C doesn't even have strings, but you would typically be using char arrays instead. All you need is a pointer to the array in order to access it. However, if you just have the pointer then you are lacking to essential pieces of information, the length of the string and the capacity of the string.

The length of the string is however by convention determined by the first NULL byte (zero termination), so it is important that there is a NULL byte within the bounds of the allocated array.

Concatenating two "strings", is not particularily difficult, it just needs to be done with care.

If you find it complicated, then you should not use C, nor should you use it for things it's not intended for.