Export compliance
Export compliance is the declaration Apple requires on every build about whether your app uses encryption, driven by US export regulations rather than by Apple's own policy.
Most apps use encryption and most qualify for an exemption. Calling HTTPS endpoints, using TLS through Apple's own frameworks, or relying on standard algorithms provided by the operating system is the exempt case. Shipping your own cryptographic implementation, or a proprietary algorithm, is the case that is not.
You can answer it once instead of on every upload. Add ITSAppUsesNonExemptEncryption to Info.plist as a boolean: false if your usage is exempt, true if it is not. With the key present, App Store Connect stops prompting when you attach the build. Without it, someone has to click through the questions each time, and a stalled release is often just that dialog waiting.
If your encryption is genuinely non-exempt, the declaration is the small part. You may need documentation from the US Bureau of Industry and Security, and Apple's own ITSEncryptionExportComplianceCode key exists to carry the resulting authorisation number.
Two cautions. This is a legal declaration you are signing, so guessing false because it makes the dialog go away is not a neutral act. And separate French declaration requirements have applied to some apps historically, which is worth checking if you distribute in France.
See also: build, Transporter, App Store version.