@sun @weeble both and neither of course.
the purpose of empathy is (multi-faceted) to teach to children via familial members the following: correct self-behaviors and detecting other's behaviors+intent+goals.
empathy needs to work between people that emotionally deeply care about each other.
a mother lifts his arm, toddler lifts his arm. they both move their arms together and touch.
it can work with more people than the ones you just care about, and that's fine, but can be stressful if overworking. if it works less, then that's autism. if it doesn't work at all, then that's severe autism/borderlining on psychopathy. good trained empathy lets a person know what another's intents are. the more you get to train your empathy related neurons, the more experience you have in correctly instinctively assessing someone's intent, desires, emotional state.

generally it starts working at age 1 year old, and there are some built-in starter simple empathy learning actions (example, showing one's tongue, basic muscle movement mimicry). Empathy works mostly on audiovisual input, speech is rather recent.

to understand someone's feelings, one needs the following two prerequisites: naturally care about person (or actively attempt to care if brought to attention), and having gone through something similar on an emotional level previously

you can read about "mirror neurons" if you want a very detailed explanation rabbit-hole.