Is an instance of an activity considered as a namespace?

I’m new with UiPath and I noticed how you could declare the scope of a variable depending on what activity you want it to be in scope with. Does that mean that each activity in UiPath is its own namespace?

It does not. Scope is defined by the sequence level of your project. For example, you can delete the sequence provided in Attach Browser and just put one activity within, but then you cannot limit the scope to just the Attach Browser activity. However, you can limit the scope if you leave the sequence in Attach Browser to the level of that sequence.