online
Describes the state of being connected to the internet or another network.
Sobald du online bist, können wir mit dem Videoanruf beginnen.
As soon as you're online, we can start the video call.

Loading your saved state.
Describes the state of being connected to the internet or another network.
Sobald du online bist, können wir mit dem Videoanruf beginnen.
As soon as you're online, we can start the video call.

The word 'online' is almost always used after a verb (predicatively) or as an adverb. It is normally not placed before a noun and declined. Instead, a compound noun is formed.
Ich bin jetzt online.
I'm online now.
'Online-' is a very productive component for new nouns in German. It is simply placed before another noun to show that something takes place on the internet.
Das Online-Banking ist sehr praktisch.
Online banking is very convenient.
To describe the state, you use 'online sein' (to be online). To describe the change into this state, you say 'online gehen' (to go online).
Ich gehe kurz online, um meine E-Mails zu prüfen.
I'll go online briefly to check my emails.
'Online' is often combined with verbs that describe an activity on the internet. Typical examples are 'online einkaufen' (to shop online), 'online spielen' (to play online), 'online arbeiten' (to work online), or 'online lernen' (to learn online).
Viele Leute kaufen ihre Kleidung heute online ein.
Many people buy their clothes online today.
digital
'online' and 'digital' both have to do with computers, the internet, and modern technology. 'online' means that something is connected to the internet or takes place on the internet. 'digital' is broader: it describes information, devices, or processes that are handled using computer technology, even without the internet. Learners can easily confuse the words because many digital things are also online. But not everything digital is online: a file on a USB stick is digital, but not necessarily online. 'online' fits when the internet connection is important; 'digital' fits when the technical form or processing is important.

Am Wochenende ist der Kurs online, nicht im Klassenraum.
At the weekend, the course is online, not in the classroom.
Beim Termin hat die Mitarbeiterin die Unterlagen digital gespeichert.
During the appointment, the employee saved the documents digitally.