Clamps are a big issue in the shop. Like chisels, they come in a variety of sizes and shapes. You will use clamps often in the shop to hold your work tight so that you can machine it and to hold it together until the glue dries. When in doubt about holding a piece of wood to work on it, use a clamp. I would rather you ruin a clamp then hit your finger or hand.
The two long and skinny clamps at the top of the picture are bar clamps. They are frequently used to clamp wood together while the glue dries.
The silver and orange clamp in the middle is a spring clamp. This is a general purpose clamp that is used to hold your work in place while you assemble.
The blue clamp in the lower left is a C-clamp. Once again, this a general purpose clamp used in gluing, assembly and some machining.
The black and yellow clamp in the lower right is a trigger clamp. Great for when you are working by yourself and need a third hand to hold something. An otherwise very versatile clamp, it is not very good for wood glue up.