Silverfish are definitely strange insects. They look like shrimp or crustaceans, and they're distressingly fast. Although they're not dangerous, they're also not much fun to have around. You shouldn't necessarily panic when you see one, but you should do something about it.

Why are lawn shrimp in my house?

If they have scuttled indoors, it could be because outside is too dry and they're chancing that indoors may be wetter (not generally the best idea, shrimps). Or conversely, it's because a heavy downpour has made their outdoor habitat too waterlogged and they're seeking moist but dryer living conditions.

What is a shrimp bug?

These creatures are not insects, but are crustaceans and go by their common name “yard shrimp” since their appearance is very shrimp-like. When disturbed in their natural habitat, seeing them jump around may remind someone of fleas or springtails. Amphipods get inside through open doors.