Hello axko, I do realize you may have already looked at the help section. The documentation is really quite extensive and helpful on working with images. If you have not looked at it you may find that helpful. You can also send a note to Duncan directly at feedback@sitely.app. He is always very helpful and answers quite quickly.
When you add an image to a web page, the image is always placed inside some kind of container - for example a box, placeholder, or wide/full-width image area.
The Fit and Fill options simply tell Sitely how the image should behave inside that container.
Fill makes sure the entire container is covered by the image.
If the image and container have different shapes (aspect ratios), parts of the image may be cropped off to avoid distortion.
Fit makes sure the whole image is visible inside the container.
Usually the longest side is adjusted to fit first, while empty space may appear around the shorter side.
Both options are designed to keep the image looking correct and prevent stretching or distortion.
If you’re using a normal image box or placeholder, you can manually resize both the image and its container by dragging the handles. However, you can only scale within the page boundaries - you can’t drag the object wider than the page itself.
A Full Width Image works differently. In this case, the browser window controls the width automatically. Because of that, you can only adjust the height of the image area in Sitely.
This also means that different visitors may see slightly different portions of the image depending on the size and shape of their browser window or device screen. Wider screens will reveal more of the image horizontally, while narrower screens may crop more of the sides.