Difference between "branch taken" and "branch executed" in gcov (GCC coverage tool)

The GCC coverage tool gcov reports two sorts of branch coverage information. One is

branch executed

another one is

branch taken at least once

Anyone knows their difference? I suppose that if a branch is executed, then it is taken as least once, and vice versa. However, gcov probably views "branch executed" and "branch taken" as two different things. Can anyone clarify? Thanks.