When two cousins are the same distance in generations from the common ancestor, the child of cousin A is called a "cousin once removed" by cousin B. This is because the child of cousin A is one generation further from the common ancestor.
Two cousins at equal distance from the common ancestor always denotes first cousin, second cousin and so forth. When generational distances are not equal, the term "removed" is applied accordingly based on distance.
When both cousin A and B have children, those children are second cousins to each other. Should the child of cousin A have a child, that child is called a "cousin twice removed" by cousin B; cousin B's child would call the new child "second cousin once removed."