What is the difference between compound, element, and mixture?

An element is the simplest substance, one which cannot be broken down into smaller parts through typical physical or chemical approaches. Elements can be found in the periodic table, which organizes and lists them out according to their properties, such as mass. Elements consist only of atoms or molecules (in other words, two or more atoms of the same or different elements that have been bound together chemically) of identical chemical properties. 
Compounds are atoms of two or more different elements which have bonded together and which can be broken down into elements via chemical means.
Mixtures are a combination of different elements and/or compounds. For example, when we add salt to water, we are making a mixture; new molecules are not produced as a result of this. Instead, they mix together while keeping their own identities intact.