Questions about suffixes like "-er" that create "agent nouns"; see also the tag "agent-nouns".
Agent nouns (see agent-nouns) are nouns denoting the performer of an action. Questions with this tag relate to the suffixes used to form agent nouns from their corresponding verbs, for example
jog + -er = jogger, one who jogs
direct + -or = director, one who directs
motor + -ist = motorist, one who motors
Some questions about their counterparts, recipient noun suffixes, may also appear. The most common recipient noun suffix is -ee.
grant + -ee = grantee, one who is granted something