Word
Log
A log is the running diary your app writes about what it did, so you can find out what happened after it happened.
Also called: logs, output, console output
Every time it starts, handles a request, or hits a problem, it writes a line with a timestamp. When something goes wrong at six in the morning, the log is the only witness you have.
Reading one fluently is not a skill you need. Finding one is. Learn where your app's logs sit on your machine and where they sit once it is online, and when something breaks, copy the lines around the failure and hand the whole thing to your agent rather than your summary of it.
The mistake to avoid: customer details and keys written into logs, which get copied and pasted around.