Originally Posted by maianhvk
Correct me if I'm wrong: I think the apps freeze in Android, but keep running in iOS?
Not by default, no - when you switch away from an app in iOS it enters suspended state where it consumes no processor cycles but is ready to continue from where it left off when it is returned to the foreground.
An iOS app can request some time running in the background if it wants to, for example to allow it to finish a lengthy task it had already started, such as a download. However the app needs to take explicit steps to make this happen.