Your photo is 2400 pixels wide, the editor says 300 PPI, and the print preview shows eight inches. Those numbers can all describe the same image. They measure different parts of the job, which is why comparing them without labels gets confusing.
Count pixels first
Pixel dimensions describe the image grid: its width and height in pixels. Print density describes how many of those pixels are assigned to an inch on paper. Adobe’s explanation of printed resolution connects those dimensions to the intended print size.
For a simple calculation, divide width in pixels by pixels per inch. A 2400-pixel-wide image at 300 PPI spans eight inches. At 200 PPI, the same pixel width spans twelve inches. Neither number is a universal quality recommendation.
A label change is not new detail
If the pixel dimensions stay fixed, changing the PPI value changes the intended physical size. Resampling, by contrast, changes the pixel grid. These are different operations, even when an editor places their controls in the same dialogue.
Before exporting, write down your actual destination. A web page needs an appropriate pixel size for its display. A printer may specify a physical size, resolution and other requirements. “High resolution” by itself leaves too much undecided.
Inspect the result where it will be used
Check small text, fine edges and gradients at the final display or print size. A file that looks impressive when zoomed out may not hold the detail you need when enlarged. Conversely, an oversized export may add download weight without a visible benefit on a small screen.
Keep a separate working original and export a copy for the destination. For the next decision—JPEG, PNG or another format—see choosing an image format by the job.