Some are external (less risky but slower), others are internal (faster but easier for anti-cheat to detect).
Downloading scripts from unverified sources (like random Pastebins) puts your device at risk of malware or account theft. How Developers Create ESP (Educational Context) For those interested in the technical side of scripting :
"You've got to be kidding me," Sam said, as he killed Tyler for the fifth time that game. "ESP script, really? That's so basic."
Most battlegrounds games have active anti-cheat measures. Using unauthorized scripts like Nex Hub or other hacks can lead to permanent account bans.