The backoffice is the "Admin" part of the Umbraco CMS tool.
A section in Umbraco is where you do specific tasks related to that section. For example, Content, Media, Settings, Users, Developer, Forms, etc. are all different "Sections" of the CMS tool. You can navigate between the different sections of the backoffice by clicking the corresponding icon in the section menu.
The Section menu is the vertical menu located on the left side of the backoffice.
Content – Where your website pages live. You create your content there.
Media – Where your images/pdf’s and files live that you use for content. You can make folders to organize it also. You can drag and drop or click and pick what you want to upload.
The Umbraco File Tree
A tree is a hierarchical list of items, which could be something like a content tree or a media tree. You can expand trees by clicking the down arrow to the left of the node. This will expand all the documents create underneath its "Parent" file.
Nodes (The "Content" of most pages)
A Node is an item which houses the "Content" in the Umbraco Tree. Most Nodes in the content section are Webpages which contain content. Other Nodes may be part of a larger piece of a website. Each "Node" will consist of a specific "Document Type" which contains field sets (or tabs) where you can apply rules about where the content can be created.
Each node can also have a number of "Child" nodes which are restricted in where they can be created.
"Parent," "Child" & "Sibling" Node Relationships
The Nodes in Umbraco are sometimes referred to as "Parents," "Children," or "Siblings" of other nodes. The Parent-Child-Sibling relationship between nodes is defined during the development phase of the website. These relationships are necessary in order to make sure content needed from specific areas of the website are trickled up or down to the correct "Parent" pages or "Child" sub-pages of a website. This also aids in not having to insert the same content in 2 different spots in a website. These relationships also define what "Types" of nodes are allowed to be created in different parts of the site.
An example of this, would be a brands "Models" node relationship in respect to each "Model Series" of the brand and each individual "Model" in that "Model Series." In this case, an individual "Model" node cannot be created anywhere outside of the "Model Series" node. This is because the "Model Series" nodes depend on the child "Model" nodes to generate content to display with the other children on the "Model Series" page, like descriptions of the model and model name. The "Model Series" page can then display bits of information about each of its children on the "Model Series" page on one larger summarized page.
In turn, you cannot create a "Model" anywhere on the site, it can only be under a "Model Series" node, which also has to be under the "Models" node.
What is a Document Type?
In its most basic form, a document type is a form containing field sets (or tabs) where you can apply rules about where the content can be created, which template(s) are allowed, backoffice icon and so forth.
Document Types can define entire pages or more limited content that can be reused on other nodes ie. SEO tab. This means that you are in complete control of what type of content can be created where.
Document Type Properties
Each field on a Document Type is called a property. A property is given a name, an alias (used to output the properties content in a template) and an editor. The editor determines what type of data the property will store and the input method. There are a wide range of editors available out of the box (textstring, Rich text, media picker and so forth) and you can customize and add additional editors.