Check - Facebook New Timeline Profile
The activity log is actually your past records. It means it will show all the records logs what you have done over Facebook. Even if you hide a story from your profile timeline the story will still appear in your activity log. This activity log is only visible to you. None your friends or anyone can view your activity log.
Check - How to enable timeline Facebook new profile
To access to your activity log by clicking on the "View Activity" button on your timeline profile layout under your cover. All your Facebook stories will be organized with time and date when and what you have done in your facebook. Example: comments, likes, shares, pokes, photos, status and others.
What things you can do in the activity log :
You can scroll through a history of all of your activities on facebook
View and approve your pending posts
Filter the type of activity you see
Choose which stories are featured on your timeline.