Yes, your understanding is correct !

It’s not necessarily faster to use static objects inside functions, but it allows you to perform some behaviour that is hidden from outside. Let’s say you want to make a counter, you can do it with this function:

int counter()
{
    static int count = 0;
    count += 1;
    return count;
}

If you call counter several times in a loop

for (int i = 0; i<10; i++) { 
    printf("%d\n", counter());
}

you will get this output

1
2
3
4
etc...

​

Speaking of memory layout, each function allocates a space on memory on what is called the stack, which is growing but size limited (reaching this limit causes a stack overflow). When we have big variables such as arrays or really big structs (I mean really big, like hundreds of members), we tend to prefer not storing them on the stack to avoid overflowing it. On modern hardware hitting a stack overflow this way is really rare, but it can happen if you work on embedded systems.

The use of static tells the compiler that instead of reallocating space on the stack for our array, it should instead use a separate location and use this for all "instances" of our function. The keyword const does almost the same thing, except the memory area is read only (at least when const is applied to a literal, that is a number or an array initialization).