differences in assigning pointers to vector

A vector of Elements

std::vector<Element> elements;

You can add Elements to it. Assuming Element has default constructor, you can use:

elements.push_back(Element());

You can get the first Element from elements using:

Element e = elements[0];

Pointer to a vector of Elements

std::vector<Element>* elementsPointer;

In order to add Elements to elementsPointer, is has to point to something valid.

elementsPointer = new std::vector<Element>;
elementsPointer->push_back(Element());

You can get the first Element from elementsPointer using:

Element e = (*elementsPointer)[0];

or

Element e = elementsPointer->at(0);

A vector of pointers to Elements

std::vector<Element*> elementPointers;

You can add Element* to the vector.

elementPointers.push_back(new Element);

When you get the items from this vector, you get Element*s.

Element* ePtr = elementPointers[0];

Pointer to a vector of pointers to Elements

std::vector<Element*>* elementPointersPointer;

In order to add Element pointers to elementPointersPointer, is has to point to something valid.

elementPointersPointer = new std::vector<Element*>;
elementPointersPointer->push_back(new Element);

You can get the first Element* from elementPointersPointer using:

Element* ePtr = (*elementPointersPointer)[0];

or

Element* ePtr = elementPointersPointer->at(0);

Using a reference

Using a reference to any of the above forms is just like using references to any other types in C++.

Use can use:

std::vector<Element> elements;
std::vector<Element>& elementsRef = elements;

or any of the other variants.