On Linux files and folders have permissions info for owner, group and everyone else. So you can set individual permissions for these.
By setting the owner to root, if you want to make your user able to read/write that folder, you must either give permissions to everyone to read/write OR assign a group to the folder, give the group permissions to read/write and add your user to that group.
If you instead set your user as the owner of the folder, you can make only your user able to read/write without other fuss.
If you are a newbie, stick to gui file manager. Can you please tell me what file manager are you using? Most of the time you can change permissions thru right click > propriety > permissions.