Container controls such as panels have a Layout property in its Properties tab. This allows you to choose how child controls for this container will be laid out.
Vertical Box and Horizontal Box are self-explanatory.
Flow will fit as many controls from left-to-right as will fit, and then continue onto the next line. This is useful for laying out an unknown amount of content, and adapting to different screen sizes such as mobile.
Column will display controls from left to right until the number of columns is reached before starting a new line. The number of columns can be set in its Layout Properties.
Field Grid is used for aligning input fields, which will be covered in a later session.