Your are actually creating two headings and one paragraph.
Similar to our English language here in HTML we have headings and paragraph’s
<h1>CatPhotoApp</h1>
The above code is clearly saying that you are creating a Heading using <h1> tag, with its default property as bold and Increased font-size .
Similarly, creating another Heading using <h1> tag, here this tag is bit decreased in its font-size comparative to <h1> tag. <p> tag in HTML .
Here this tag is not bold and less in its font-size comparative to heading tag’s by default .