system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does congress have an approval rating of 5%, but 90% are reelected? (confused non-American here)
gpt
In order to get elected, a person just needs the majority of the vote.  If 51% of people vote year in and year out for the same person, they'll be elected 100% of the time, but still only have an approval rating of 51%

Now imagine 2 people from 2 states form the entire lawmaking body.  Each gets in with 51% of the vote.  Each is still elected 100% of the time.  But, they are from different parties and must agree on everything in order for new laws to be passed.  On many issues, they disagree and nothing is done as a result.

If you ask each state, 51% will still approve of their senator, but 0% will approve of the lawmaking body, since nothing is being done that they want to get done.

This is how you can get an approval rating of 5%, with 90% being reelected.  A reelection says the majority of people from a certain area believe this representative meets his/her criteria, but a congress approval says that all the representatives together do not meet their his/her criteria.  It's a misleading stat, and a result of having a two party system.