The `select()` method selects one element from the document. It takes an argument for the name of the element you want and returns an HTML node for the first element in the document that matches the name. Here's an example:
The above example finds the first anchor tag on the page and saves an HTML node for it in the variable `anchor`. You can use the selection with other methods. The "d3" part of the example is a reference to the D3 object, which is how you access D3 methods.
The `append()` method takes an argument for the element you want to add to the document. It appends an HTML node to a selected item, and returns a handle to that node.
The `text()` method either sets the text of the selected node, or gets the current text. To set the value, you pass a string as an argument inside the parentheses of the method.
Use the `select` method to select the `body` tag in the document. Then `append` an `h1` tag to it, and add the text "Learning D3" into the `h1` element.