"I'm going to swap out the battery in this radio for a new one". You need to use the phrase in contexts where there is a sense of taking something out and putting something back in its place. For example it wouldn't really work for a library book "I'm going to swap out this book for another" - you'd just say, "I'm going to swap this book for another".

In US usage, for the last few decades, it refers to troubleshooting a piece of electronics. To "swap out" a part means to take it out of a piece of equipment and put a new part in. "Swap" means exchanging on part for another. You "swap out" the old part--you are taking it out of the computer--and you "swap in" the new part. You are putting it in, as part of the "swap." For example, if you suspect there is a problem on a graphics board, you swap it out for a new graphics board that you know is good. If the computer works, you have proved the old board was bad, AND you have fixed the computer. If the computer still doesn't work, you know that the old card was good, and you swap it back in.

It means exchange.