Here's an example, I have looked up many times (like just now), which checks whether a string is empty:

var=""
if [ -z "$var" ]; then
    echo "empty"
else
    echo "not empty"
fi

Why -z? I have no idea. I will also routinely forget the ]; then part. I believe, if you write the then onto the next line, then you don't need the semicolon. And then someone's probably gonna tell me to use double-brackets [[ ]] instead, which probably does something.

Arguably, I never fully learned Bash syntax, but it also is just a stupid if-statement. There shouldn't be that much complexity in it.