You would feel the ground shake in a magnitude 3 quake.
Sometimes there are many small earthquakes before the big one. These small ones are called foreshocks. After the big earthquake, the mainshock, again there may be many small quakes. These are called aftershocks.
You may not notice a magnitude 2 quake.
4 out of 5 of the world's earthquakes take place along the rim of the Pacific Ocean, a zone called the Pacific Ring of Fire.