Is Activity a step, a method or something else?

[yallready]

I can't find in any of the samples or documentation where "get-approval" activity's implementation is. If I understand this correctly, "get-approval" is the name of an activity which is a step or a method? Can someone provide an example please?

The workflow will wait for the result of an API call which checks for a status before the workflow continues. Is using an Activity the correct way to achieve this?

builder
    .StartWith<HelloWorld>()
    .Activity("get-approval", (data) => data.Request)
        .Output(data => data.ApprovedBy, step => step.Result)
    .Then<CustomMessage>()
        .Input(step => step.Message, data => "Approved by " + data.ApprovedBy)
    .Then<GoodbyeWorld>();

var approval = host.GetPendingActivity("get-approval", "worker1", TimeSpan.FromMinutes(1)).Result;

if (approval != null)
{                
    Console.WriteLine("Approval required for " + approval.Parameters);
    host.SubmitActivitySuccess(approval.Token, "John Smith");
}