In terms of communication, most online platforms of teaching and learning are

Most online teaching and learning platforms are asynchronous, letting learners open recorded lectures and materials at a time of their own choosing rather than at one fixed live moment.

Synchronous communication needs everyone present together, as in a live video class, which most platforms do not require.

One-to-none is not a recognised communication mode and carries no real meaning here.

Being tied to a specific timeframe describes synchronous learning, the opposite of the flexible access these platforms give.

Asynchronous delivery suits learners in different time zones and with different schedules.

Recorded videos, discussion-forum posts and email are common asynchronous learning tools.