It means to conclude or to wrap up. It's in the concluding paragraph. Example: All in all, the pyramids in Egypt took a long time to construct.

It's a phrase to sum up a lot of information. 'All in all' is synonymous 'with all things considered,' 'everything considered', ' on the whole'. Examples: All in all, it has been a good day. (The total sum of the day has been good.) All in all, that performance was great. (The total sum of the performance was good) I hope this helps, rather than confuses :)