Dynamic Object vs Non dynamic object in C++ [duplicate]

When do you want to use a dynamically allocated object such as, https://leetcode.com/problems/design-twitter/,

• Your Twitter object will be instantiated and called as such:
• Twitter* obj = new Twitter();
• obj->postTweet(userId,tweetId);
• vector param_2 = obj->getNewsFeed(userId);
• obj->follow(followerId,followeeId);
• obj->unfollow(followerId,followeeId);

[ie pointer to a new object]

or a (static?) object such as, https://leetcode.com/problems/flatten-nested-list-iterator/:

• Your NestedIterator object will be instantiated and called as such:
• NestedIterator i(nestedList);
• while (i.hasNext()) cout << i.next();

[ie standard object initialization]