The difference between one tick and two ticks is displayed in the lower right corner of texting.

The difference between one hook and two hooks after Whatsapp iphone sends a message is as follows:

A gray checkmark indicates a non-delivery status, which may be that the network is not good enough to send. If this has always been the case, it is not excluded that the other party uninstalled the app, or it may be that the other party's mobile phone can't get online.

Two gray checkmarks indicate sent and unread.

Two small blue checkmarks indicate that it has been sent and read.