/Magazine
-Motoring
-aricle1
-aricle2
-Lifestyle
-aricles
What are the list of channels I should create in ee, and how do I relate them
url will be
www.example.com/magazine/motoring/car-article
Save yourself grief and purchase Structure which will make this a breeze and allow you and your client a visual interface onto the content.
Failing that, I need more information on the individual data. If the raw data for motoring articles is identical to Lifestyle articles (e.g. they have a title, content, images) then you only need 1 channel "Articles" and you could segment with categories (Motoring & Lifestyle). If Magazine, Motoring & Lifestyle are more than just landing/listing pages and hold unique content themselves (not the articles), then they might be a second channel called "Content".
Channels are groups of data, beyond their subject matter there's no real difference in the data between Lifestyle and Motoring, so although you can, it doesn't make sense to split them into different channels. If the client requests a new group (say Sport), using multiple channels is inflexible and you'll then need to build a new channel, template structure, templates, etc. whereas if it's all articles, the client themselves can create a new category called "Sport" and the system will just work.
You ask how do I relate them, but don't explain how they're related, unless you're referring to the parent "Magazine". Which isn't really a relation, just a container.
Assuming you have one channel "Articles", you have a template group called "Magazine" (which is the first part of your URL), the index template would be your landing page if segment_2 is empty {if "{segment_2}" == ""}. If segment_2 is not empty but segment_3 is empty (which means the user is on Lifestyle or Motoring) {if "{segment_2}" != "" && "{segment_3}" == ""} the index can embed or serve up the listing pages for the individual categories or entries (if they're content pages with unique content beyond the articles within) Motoring & Lifestyle. You can then approach the listing pages (Motoring & Lifestyle) in many ways, either templates in the template group (magazine/motoring) which isn't flexible and relies on new templates created that contain duplicate code, or via the index template with embeds to keep things neat and segment as categories e.g. {embed=content/{category_url}}.
With ExpressionEngine there are many ways to approach it, and the "right" way is normally down to the individual developer. The "best" ways are those that are clean, easy to follow and flexible for expansion in the future.