Generally, semi-hollow bodies refer to those archtops with thin bodies and a solid center block a few inches thick running through the body. Advantages are less feedback and more sustain than a hollow body as the guitar functions more or less like a solid body with hollow wings. So it has the disadvantages of a tinny acoustic sound and heavy to hold. The design is credited to Gibson's ES-335 and is used in many models, including the Guild Starfire IV.
Hollow bodies are more varied in design, but generally are 3" or more in thickness, though thin models, like the Starfire III, have no blocks. Some archtops, like the X170, have a smaller block that is fitted between the top and back under the bridge. This reduces feedback while compromising the acoustic sound a little.
The other extreme is to design the archtop with as little obstruction to the acoustic sound as possible. These are primarily jazz guitars where the pickup is "floating" - that is, mounted to the fingerboard so it doesn't touch the top. Tone and volume controls are mounted on the pickguard as well.