Ask yourself this question, as an individual human being, are you as whole organism, a compound? element? or mixture?

Guess the answer is fairly obvious, yes we are mixtures! Our body is a big soup of blood, body fluids, organs, tissues and cells that are also mixtures of their own.

Most things in this world are mixtures of various compounds and elements.

This concept of elements, compounds and mixture is a topic usually handled at lower secondary level science in the schools. Students often are not so ready to be able to tell how the various substances around them are classified. 

Mixtures are material systems that consist of 2 or more different type of substances blended into each other. The components are not chemically combined. aka no chemical reaction was involved to lead to the formation of the mixture.

Compounds are strictly speaking molecules that is made up of 2 or more types of elements chemically combined. You can write chemical formula to them. There are much stricter rules associated to the formation of compounds, such as the percentage composition by mass.

Elements, well are all the names you see on a Periodic Table. They are the basic chemical units of matter.

Why bother to classify this anyway?

There is a point in doing this, people want to work with the materials they get and make new things. In order to do so, people often need to know the nature of the materials and how it works. This in a sense led to the beginnings of chemistry where people start to discover that not all things around us as easily separated into its parts.

Some stuff need to be purified from their original source form which can be mixed or chemically combined. Different techniques are required to obtain the components.

Mixtures only need physical separation techniques to get separated. We need to get pure salt from the sea. Singapore also depends partly on reverse osmosis for clean water.

Compounds need to be separated using chemical techniques. We need to get pure iron from iron ore. 

This is actually so important in chemistry application that this has to be taught in both lower secondary science and upper secondary chemistry.