  Our understanding of stellar dynamos has largely been driven by the phenomena
we have observed of our own Sun. Yet, as we amass longer-term datasets for an
increasing number of stars, it is clear that there is a wide variety of stellar
behavior. Here we briefly review observed trends that place key constraints on
the fundamental dynamo operation of solar-type stars to fully convective M
dwarfs, including: starspot and sunspot patterns, various magnetism-rotation
correlations, and mean field flows such as differential rotation and meridional
circulation. We also comment on the current insight that simulations of dynamo
action and flux emergence lend to our working knowledge of stellar dynamo
theory. While the growing landscape of both observations and simulations of
stellar magnetic activity work in tandem to decipher dynamo action, there are
still many puzzles that we have yet to fully understand.
