I think you are asking for a simple explanation about how elements, compounds, mixtures (and types) are different from each other.
An element is the simplest type of substance. It is made of only one type of atom and cannot be divided into simpler units. Take water for example. It is made up hydrogen and oxygen. But what are those made of? They are made of hydrogen and oxygen atoms. They can't be broken down further. Gold is an element. What is gold made of? Gold. It's made of gold.
If you take two or more elements and chemically join (bond) them together, then you have a compound. Water is an example of a compound. As is carbon dioxide (carbon and oxygen) and glucose (carbon, hydrogen, and oxygen).
If you take two or more elements or compounds and mix them together but do NOT chemically join them, that is a mixture. A lot of times an observer can see the different parts that make up a mixture. Trail mix or pizza are tasty mixtures. You can see the individual bits, and if you wanted to, you could separate them using physical means.
Heterogeneous mixtures, homogeneous mixtures, solutions, and alloys are all different types of mixtures. A heterogeneous mixture is a mixture that isn't very well mixed. Trail mix or pepper for example. A homogeneous mixture is a well mixed, uniform mixture. Milk for example. Chances are the jug of milk that you have at home even says the word "homogenized" on it. Solutions are a lot like homogeneous mixtures. In fact, I had a teacher one time say that solutions are just really really well mixed mixtures. It's a bit more than that though. A solution has one substance completely dissolved and evenly distributed throughout another. Separating the two could be done, but it's more difficult that separating a mixture. Kool-Aid is a good example. So is the air that you are breathing.
An alloy is a mixture. It is a homogeneous mixture, but the reason it is different is that the main ingredient to an alloy is metal. Cast iron for instance is not made of pure iron. It is mainly iron with carbon mixed in. It's an allow. Stainless steel is a common alloy as well.