Prev/Next
When you view an entry in the context of a listing, there will be a navigation block above the title of the entry that allows you to view the previous or next entry of that listing without first needing to return to the listing.
Note: if you view a log entry outside the context of a listing (perhaps you arrived at it by following a link from your email inbox), then the Navigation block will not be available.
Interpretation of Previous and Next
If the entries of the listing were by date in descending order (the default), then Next means the next most recent listing in time and Previous will move to the immediately older item in the listing, just as one would expect. However if the prior listing of entries was not the default, then Next will mean move up through the listing and Previous will mean move down through the listing. For example, if the listing were sorted by title in ascending alphabetical order, the Previous moves down the page (A->B->C), while Next would move Up the page (C->B->A).