What is the difference between Sickle Cell Anemia and Sickle Cell Disease?

They are the same thing. Disease is a misnomer. It is not contagious. It is an anaemia caused by a defect in the gene which is used to encode the beta globin chain of haemoglobin, resulting in haemoglobin S (HbS) being produced, instead of HbA, which is normal adult Hb. As you read, it is a substitution of Glutamine to Valine. If this is inherited from both the Maternal and Paternal sides of the family is results in Homozygous HbS (SS), which results in the serious, life threatening state, because there is no normal Hb being produced, and HbS results in large red cell destruction when stress conditions occur, such as illness. If the defective gene is inherited from only one parent, then a heterozygous condition results (AS). This generally does not cause serious anaemia, and confers some resistance to malaria, hence its persistence in the population. When a malarial parasite enters the cell, the entire red cell sickles, and it, and the parasite, is destroyed by monocytes.
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EDIT: sometimes Sickle cell anaemia is used to refer to the heterozygous state, with disease referring to the homozygous state. But in reality both state result in anaemia to some extent.

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