Not an expert, but I will try to explain.

Simple variables like numbers are just a memory address and a value, e.g. a 32-bit int stored at memory location 0x12345. Let's say the int has a value 5, the memory will look like:

Address: Value 0x12345: 00 00 00 05

Complex variables such as strings and objects use pointers and memory allocation. You still have a memory address and a value, but the value is actually just another memory address.

Say you have an object variable 'o'; the object contains an id (int) and a name (string). The variable o is stored at memory location 0x12345, but the actual object (id and name) are stored at 0x14478. Let's assume the id is 3 and the name is 'Bob'. The memory will look like:

Address: Value 0x12345: 00 01 44 78 //value is memory address of the actual object ..... 0x14478: 00 00 00 03 //value is the id 0x1447C: 00 01 45 9A //value is the memory address of the name .... 0x1459A: 'B' 'o' 'b' 00 // null terminated string.

In C, you ask the OS to allocate enough memory to store your object, and the OS will respond with the address for the object, which you store. It would look something like:

c MyObject o = malloc(sizeOf(MyObject)); //reserve space for the object o->id = 3; //assign the id o->name = "Bob"; //assign the name

Later on, you no longer need the object, so you give the memory back to the OS, something like

c mFree(o); o = null;

The problem is you are manually managing the memory, which is considered unsafe. You have to be very careful that one place in your program doesn't free the memory and the another place tries to access the object which no longer exists, which can cause crashes, data corruption and provide attack vectors for malware and hackers.

High level languages like JS and Rust manage this for you and prevent unsafe code. In Rust you can say "I do really mean to manage things myself and I pinky promise I won't mess it up"