Tropes listed in the Wiki Tropes index are being discussed at the Trope Repair Shop. Click the link here to join the discussion.
When faced with five subtly different things, would you rather see one page with a general description of all five, or five pages precisely describing one entry each? If the first, you're a Lumper. If the second, you're a Splitter.
For example: A Splitter is someone who thinks that this page should not exist. There should be separate pages for "Lumper" and "Splitter".
A lumper also wants to get rid of this page, but by merging it with a bunch of other pages to create a new page called "Common Wiki Wars".
The way Tropers handle this deep philosophical divide is for splitters to write finely-distinct entries and for lumpers to write overview entries that list the "splits". We call those lumper pieces "indexes" or Super Tropes, and each of the splits is a Sub-Trope.