我需要一些帮助来理解一些涉及C++中链表的代码

#include <iostream>

struct Node {
    int data;
    Node* next;
};

class LinkedList {
public:
    LinkedList() : head(nullptr) {}

    void append(int data) {
        if (!head) {
            head = new Node{data, nullptr};
        } else {
            Node* current = head;
            while (current->next) {
                current = current->next;
            }
            current->next = new Node{data, nullptr};
        }
    }

    void display() {
        Node* current = head;
        while (current) {
            std::cout << current->data << " -> ";
            current = current->next;
        }
        std::cout << "nullptr" << std::endl;
    }

private:
    Node* head;
};

int main() {
    LinkedList list;
    list.append(1);
    list.append(2);
    list.append(3);
    list.display();
    return 0;
}

void display() {
    Node* current = head;
    while (current != nullptr) { // 检查当前节点是否为空
        std::cout << current->data << " -> ";
        current = current->next;
    }
    std::cout << "nullptr" << std::endl;
}

~LinkedList() {
    Node* current = head;
    while (current) {
        Node* next = current->next;
        delete current;
        current = next;
    }
}