An arrest is basically a police officer's opinion that you are guilty of something. And it is very subjective from officer to officer. One officer might arrest you for something, while another one would just let you go. It's all subjective.

So an arrest is nothing major.
Now a conviction is different.
That means in a court of law, either in front of a judge and/or jury, you have been both tried and convicted of a crime so that is on you record.

But an arrest is just a preliminary thing.
For instance, someone can be arrested for being intoxicated. They handcuff them, put them in a cop car and drive them to detox for twelve hours or so. When they are sober, they are released and it is not even on their record.

That is probably what happened to you.

They arrested you, but didn't put you on the judge's docket because they had "real" cases to tend to. lol.