system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the difference between Drive, 3, 2, and 1, in an automatic car?

Very confused about this.
gpt
When you choose Drive, you are telling the transmission to choose whichever gear it feels is most suitable for the driving condition at any moment.  When you choose 1, you are limiting the transmission to the use of first gear only.  2 allows the use of first and second; 3 allows the use of the first three gears.