The term Pokémon collectively refers to the fictional species that have made appearances, like normal animals can be grouped into different types. This series of caches covers a couple of the different type.
The Psychic type has few outright strengths, however, it also has few weaknesses. In the first generation it ended up being massively overpowered, mainly due to a complete lack of powerful Bug moves, its only weakness. Furthermore, a mistake meant that Ghost-type moves had no effect on Psychic (although this only affected the low-powered Lick)..
Note the clue in the lid to work out the mystery cache location of GC6PJV1 (might want to look this up before attempting to see what you might need to help solve).