system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the difference between a Jazz Bass and a Precision Bass?
gpt
The J bass has a pickup on the bridge (bottom part of the guitar where the strings connect) and near the neck (long skinny part where you push the strings to changes notes).  

The p bass only has a pickup near the bridge.  The pickup is the part of the guitar that "hears" the sting vibrate and turns it into a signal for the amp.  On the jazz bass you can adjust the volume of each pickup on their own so it gives you a lot of options in how it sounds.  Because the pickups are in different spots along the strings they will hear slightly differently and give the sound a different tone or color.  As an aside, a lot of times j bass players will just match the level of both pickups because it rejects a buzzing sound that happens with single coil pickups.  But by plucking near each pickup you can change how the notes sound.

The p bass is a little more limited in that sense in that it only has the single pickup, but it's not necessarily a bad thing, just a difference in how the bass works and plays.