The main feature this mod adds is mayonnaise. You can find multiple mayonnaise related items around the world (most are in the new mayonnaise biome) which can be used to make new food, armour and tools. This mod also adds uranium which can be radioactive, and you can mix it with mayonnaise to create some questionable consumables. It also adds some helpful features like escalators. These are a variant of stairs that increase the speed of someone who is walking on it.
There are quite a few other hidden features that I'll let you discover...