What are these folders for? Can I remove them? How?

Question

In a folder on the SVN server/repository that is designated for our project, there have appeared the following folders:

1. branches/
2. conf/
3. db/
4. hooks/
5. locks/
6. tags/
7. trunk/
8. README.txt (file)
9. format (file)

We have all the code in the trunk folder. There were, as far as I can remember, only 3 or 4 folders earlier.

Within the trunk folder, too, there are now these folders.

1. OurCode/
2. conf/
3. db/
4. hooks/
5. locks/
6. README.txt (file)
7. format (file)

I understand many of these folders or files are not necessary, but I can't be too sure.

My questions are:

1) What are each of these files and/or folders for?

2) Which are the ones that are not necessary?

3) How may I remove them from the server repository?