A gadget is a section displaying some content on your homepage or in your category. Each gadget has its purpose and its settings. You can add gadgets to your homepage by going to "Layout" >> "More Gadgets...". You can add gadgets to any category by going to "Tools" >> "Add Gadget"
Each gadget has a hover "Settings" button which gives you a quick access to the gadget's settings. Apart from this button, there are some specialized buttons which are rather self-explanatory. The ones wanting a description are the arrow buttons which move a section up and down respectively. Always check out the "Settings" button since it usually contains all of the section's customization options.
BlueMelon currently offers the following gadgets:
Text gadget, which allows you to place an arbitrary text on your homepage. You can add as many texts as you like. Standard and Business account users may use some HTML and links within Text gadgets.
Single Photo gadget displays a single photo of your choice. You can choose to add a title or a description. The photo can be displayed in 400x300, 600x450, or 800x600. You can align the photo to the left, to the right, or center it horizontally.
Album Preview gadget displays up to three rows of photos from a selected album. You can also adjust the size of the displayed photos and add a title.
The Youtube gadget displays up to three Youtube videos in a row. You can choose the video's alignment and dimensions.