On OpenOCHem, you'll be working with many two-dimensional (2D) structures and reactions. While we can only interact with these structures in two dimensions (you can't rotate them out of the plane of the paper or computer screen), we can still represent their three-dimensional (3D) nature in 2D. Learning to draw and interpret 3D representations on a 2D surface is crucial. It's similar to the perspective drawings you might have encountered in drafting or art class.
For example, consider the structure of L-alanine below. It's perfectly fine if you don't yet know what alanine is. The bold wedge pointing to the H atom indicates that it's projecting toward you, while the dashed wedge pointing to the NH₂ group shows it's receding away from you.
L-Alanine