Lemonade is a mixture because sugar, water and lemons are combined together without a chemical reaction taking place. The bonds of the substances can't combine with one another, instead the three items are mixed up.
A compound is a pure substance that is composed of the atoms of two or more elements. These atoms can be combined in fixed ratios to form compounds. An example of a compound is when baking soda is combined with vinegar or when flour and eggs are combined together in a recipe. A mixture occurs when two or more substances blend together to form something new without a chemical reaction.