system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why I can send/be sent a text message that won't appear until hours later?
gpt
Text messages are "store and forward" - they don't go directly from your phone to the other phone.  And although they're not guaranteed delivery (they can and sometimes do just get lost), they do get retried when they fail.  Sometimes the phone the message is going to happens to be unreachable the first time, so the message gets retried a little bit later, and so on.

Now add in the fact that text messages are kind of fit into the little unused spaces in the data network in between more important activity (like phone calls).  So they usually have to wait at least a little bit before there's a space to forward the to the next spot on the network, and on towards the phone they're being sent to.  Delays are common.