I've been following lots of meteor examples and working through discover meteor, and now I'm left with lots of questions. I understand `subscribe` and `fetch` are ways to get "reactivity" to work properly, but I still feel unsure about the relationship between find operations and subscriptions/fetch. I'll try to ask some questions in order to probe for some holistic/conceptual answers. 

**Question Set 1:**

In the following example we are fetching 1 object and we are subscribing to changes on it:

```
Meteor.subscribe('mycollection', someID);
Mycollection.findOne(someID);

```

*Does order of operations matter here?*  

*When does this subscription "expire"?* 

**Question Set 2:**

In some cases we want to foreign key lookup and use `fetch` like this:

```
MyCollection2.find({myCollection1Id: doc1Id}).fetch();

```

*Do we need also need a `MyColletion2.subscribe` when using `fetch`?*  

*How does subscribe work with "foreign keys"?*  

*Is fetch ~= to a subscription?* 

**Question Set 3:**

*What is an appropriate use of `Tracker.autorun`?*  

*Why/when should I use it instead of subscribe or fetch?*