By default, Discover shows you all the newly-created content on your network first. There are various other sorting options you can use, designed to make it easy for you to find the specific content you're looking for.
When you click the Sort By list on Discover, you'll see the following sort options:
To sort the content from oldest to newest, select the Old sort option.
To show content from A-Z or Z-A, select the A-Z or Z-A sort options, respectively. This is particularly effective when looking for content the title of which you can only remember parts of.