They are all template helpers with the following main characteristics as described in emberjs guides.
(http://emberjs.com/guides/templates/rendering-with-helpers/)

1.{{outlet}} - Renders a template based on the route determined by the router. Based on the route the corresponding controller and view are used. This is useful when rendering contents based on the route, which is the most common case.

2.{{outlet NAME}} - Provides the ability to specify in the route where exactly to render the content. Useful when trying to render contents from more than one templates for a route.

3.{{render}} - Similar to outlet but the controller/view/model can be specified directly or indirectly from the helper. Useful when required to render content from more than one template with the ability to override the context (view/controller) and model. If model is specified it uses a unique instance of the corresponding controller, otherwise it will use the singleton instance. Useful when required to overide the route's context and model, while rendering multiple template contents.

4.{{control}} - Works like render, except it uses a new controller instance for every call, instead of reusing the singleton controller. When using render it is not possible to use multiple render for the same route without specifying the model, for that case the control should be used. Useful to support new instances of a controller for every template content rendered.

Update: Control helper has been removed https://github.com/emberjs/ember.js/commit/86eecd7ef7cdc7d2ea6f77b3a726b293292ec55d .

5.{{partial}} - Takes the template to be rendered as an argument, and renders that template in place. It does not change context or scope. It simply drops the given template into place with the current scope. So no view class is specified for the partial. Useful when it is required to break a template into template modules, for better control or reusability, without creating any view classes.

6.{{view}} - This works like partial but a view class is provided. The view class specifies the template to be used. Useful when breaking a template into modules but requiring a view class e.g. for event handling.

7.{{#view}} - There is also the block form of the view helper, which allows specifying the template of the child view inline with the parent view template. (http://emberjs.com/guides/views/inserting-views-in-templates/)