How to use of const keyword with pointers?

Hi, i am learning C++ programming and I want to figure out the use of const keyword with pointers. I have explored many programming forums to get a satisfactory solution but didn't get it. I hope some of the tech experts in this community can help to figure out my issue.

As you would with any other type.

There are three variants:
1) const T* p
2) T* const p
3) const T* const p

1) says the pointer points to const. Thus:

int x;
const T* p = &x;
p = &x; // OK - reassign contents of variable
*p = 0; // Error - can't change value of what it points to

2) says that the variable itself is const. Thus:

int x;
const T* p = &x;
p = &x; // Error - can't change value of the variable
*p = 0; // OK - can change value of what it points to

3) is basically a combination of both.