ExpressionEngine content is contained in channels and in these channels are individual entries. You could think of a channel like a collection of content items.

It makes sense to create channels that reflect an area or topic that you are addressing.  For example, you might have channels like this:

• About
• Contact
• Products
• Blog items

So you could have a collection of entries in about with each one describing a member of staff or pieces describing why your organisation does what it does.

Channels also have custom fields allocated to them which means that the entries in a channel can have the same structure as each other.  This makes a lot of sense for a product channel where you might have fields like:

• Description
• Product number
• Price
• Product Image(s)
• Summary

I often find that there are additional channels that are needed for content that does not fit the structure of the channel that you would automatically associate with this type of content.  e.g. If you have products that are vastly different from each other; it doesn't make sense to have loads of redundant fields just because you want to jimmy them into the same channel.  It is also tricky if some fields need to be set to required for one product type but not for the other.  That's when I would create an alternate channel.

In face any listing page feels like it should go in the channel with its children.  You expect the blog listing page to use content from the blog items but you probably want to add in a paragraph summary or similar to that page.  You could use a global variable to deal with the summary text but that then becomes awkward as you would normally look for big chunks of content in a channel entry.  So I opt for a listings channel or landing pages channel because I feel that makes more sense for the person updating the website.

Another channel type that I think works very well with ExpressionEngine is a promo channel. I like this because it allows the web administrator to create promo content that can then be shared accross entries using the relationship field.