The chlorophyll in live foliage reflects infrared light strongly, so it appears bright in infrared photographs. (Or, in false color IR, it appears magenta/pink or whatever color is used to represent IR.)

Infrared light can also have unpredictable interactions with paints, dyes, pigments, etc. resulting in printed designs appearing different. I have a long-running project photographing flags in infrared with widely varying results. IR is also more resistant to UV haze (since it’s at the other end of the near-visible spectrum) and can sometimes pass through sunglasses lenses.

Other things will also look funky in IR, such as the sky (dark as with a deep red BW filter) and human skin and eyes.

UV photography can get even funkier, but I haven’t gotten into that yet.