Content in Posts to link

Hi, I would like to know how to organize our post & link the content in the post to a sub post/page that has supporting contents to the initial post.

in laymans term, i would like to create certain post and have a bundle of content. after that, i would like to link part of the contents to a sub-content to support the main content. Do i have to create a catagory for those sub-contents or just create another post/page?

Cause I thought if I do create another post/page.. it would be very messy for my blog & I want to keep it as neat as possible.

I would appreciate any ideas. thank you.