An "assignment" is any activity where you'll have to do something and turn it in or share it. This could be a paper you submit, a quiz you take, a discussion you post to, or a group project. It does not include readings (they are assigned to you, but you don't usually have to turn anything in at the end).

Happens at different times. For example, many online courses use asynchronous discussions, meaning everyone can participate at different times. One person might chime in at 11 p.m. on Wednesday, while another might answer on Thursday morning.

physical computer devices, like a computer, monitor, or other devices you'll need.

Someone who monitors an exam while it is being taken, to make sure that all exam procedures are followed. This usually happens in person, but it can sometimes happen through an online service.

programs or applications (apps) that you need to install on your computer/device

The document that explains course policies and procedures, usually presented at the start of a class. It will likely include contact information for your instructor, institutional policies students have to comply with, and grading information.

Happens at the same time. For example, if an online class requires everyone to be online for a live lecture at 9 a.m. on Friday, that's a synchronous element to the class.