Solids are a type of matter than is extreme stiff, the atoms cannot move on their own. Solids are very visible and some solids can bend.
Liquids are a type of matter that can flow and change shape. The atoms can move on their own a little bit, but are still very close.
Solutions are a type of matter consisting of matter dissolved inside a liquid. This means that it can flow and change shape like a liquid, but react chemically like the matter dissolved inside it.
Gas are a type of matter than is free and can even change volume. The atoms can move all they want, they might not collide, but it is possible they will.
Plasmas are a type of matter that is ionised, meaning that its atoms have more or less electrons than they would normally. This means that they can be moved around by magnetic fields. Plasmas are usually found only at extreme temperatures, such as in stars.
Dark matter is the second most common thing in the Universe, only beaten by dark energy. It is about 8 times more common than visible matter.