Your human wants you to walk on the lead at the same pace as they do, next to them.
There is benefit in doing this, but no real problem if you forget yourself from time to time and stop for a sniff. Don’t be surprised if they over-react though and make sure that you make it clear that you deserve a treat for doing this regularly. I talk about how to do this elsewhere, but my main trick is to walk just in front of them facing them looking all lovey dovey. It often works. If it doesn’t work after 20 seconds though, quit, it gets undignified!