A clamp is a device that is used to hold something tightly. Clamps can be used to hold things such as two pieces of wood together so that they can be worked on without them slipping apart. You often clamp materials together after they are glued, to stop any movement before the glue has completely dried.
Clamping generally means something means holding it so that it cannot move.
A lava lamp contains wax, water and a light which acts as heating element. As the lamp gets warm, the wax melts and starts to rise. As it rises it forms interesting shapes, which makes lava lamps fun to watch. Lava lamps come in all sorts of different colors, and the wax and water in them also come in different colors.
A ramp is a surface that is sloped to make it easy for things with wheels to get between a low place and a higher place. The ramp in the photo is for people to get in and out of a truck.
Ramps are often used inside multi-storey car parks so cars can drive up to the top. Ramps are also used as well as stairs to get into a building. People can walk up stairs easily, but ramps are needed for people who are in a wheelchair, for people with prams, or for anyone who simply has trouble climbing stairs.