Hi I am new and need some help with the code

What does this mean
The main element should have two paragraph elements as children.

Hi @tOfu, welcome to the forum.
The main element is the element that has the opening tag <main> and closing tag </main>.
Now, an element (the parent) can have children, which are other elements written between its opening and closing tag. Something like this:

  <child1>...more stuff</child1>

Some elements have self-closing tags (like the child2 example. One of the elements that fall in this category is the img one), some need both the opening and the closing tag (like child1. One of these elements is the paragraph one (<p></p>)).