Wikipedia provides user pages to facilitate communication among participants in its project to build an encyclopedia.
If your username is Example:
The Special:Mypage and Special:Mytalk special pages will take each user to her or his own user and user talk pages, respectively. Others will not be able to find your user page using Special:Mypage, they will be able to visit it only by going to User:Example (for the example user).
Details about you generally should not go in the main namespace, which is reserved for encyclopedic content.