Explain clearly..

What are kind of factors that decide the angel curve? In microeconomics, the Engel curve describes how a household's spending on a particular good or service changes with household income. The shape of the Engel curve depends on a number of demographic variables and other consumer characteristics. The Engel curve of a good reflects its income elasticity, indicating whether the good is inferior, normal, or luxurious. The empirical Engel curve is nearly linear for some goods and highly nonlinear for others. For normal goods, the Engel curve has a positive gradient. In other words, as income increases, so does demand. In general goods, there are two possibilities. Although the Engel curve is upward sloping in both cases, the Engel curve for necessities bends on the X-axis and the Engel curve for luxuries bends on the Y- axis