Its really up to you - do both! You can alternate on different days, find out what works for you. Jogging is going to exercise your heart and cardio repiratory system, but if you don't enjoy jogging, or you are out of condition, then walking would be fine. I personally wouldn't recommend jogging every day. Two to four times per week is plenty enough to improve health and fitness, and those running muscles sometimes need a rest - how about walking on the other days.
And then there is the HIIT approach, where you can, for example, alternate between fast walking and sprinting in one session. If you search the Web, you should be able to find a free HIIT programme.