What’s a Taxonomy?
The term Taxonomy can be somewhat confusing (and it’s not related to tax at all!). Taxonomies are basically the way WordPress sorts things out. For example, categories and tags are taxonomies, they just have a familiar name so people mostly recognize them as Category or a Tag, not Taxonomy. It’s even in the description of one of your post’s tags:
Since WordPress 2.3, plugin and theme authors have had the ability to
create custom taxonomies– essentially specialized “categories”– to
help organize information.
Can i use them for storing content?
As you’ve probably already noticed, taxonomies don’t contain any content. They are just used for sorting things out, just like the labels on your delicious jars of jam.
So, if you have a blog, that for example contains both musics and articles, you need to create 2 different post types. This way, you can choose different templates for each of them, run custom queries, etc.
Do i need to create both Taxonomies and Custom Post Types?
To sort these 2 post types, you can use the usual categories. But, if you are going to work neat, you should create a taxonomy for each of them, and assign each post to its related taxonomy. This way, if you come back later and try to do a bulk action, you can easily deal with a post type without even going near the other one.