LaTex lets you break the document down into chapters, sections, subsections, subsubsections and paragraphs. By default subsubsections and paragraphs are not numbered or included in the table of contents. Sometimes this might be desirable. However, I usually find that in cases when I do not need them numbered, I usually never use them (ie. my documents are broken down by chapter, section, and subsection only). At other times, when I desire more granularity, I actually want subsubsections to show up in the TOC and have distinctive headings and numbers.
To enable this you will need to put 2 lines of code somewhere in your preamble:
The first line enables numbering of subsubsections. The second line includes subsubsections in the table of contents.
Btw, if you need to break down your document even more you can switch 3 to 4 in these lines to enable numbering for paragraphs.
[tags]latex, subsubsection, paragraph, section, numbering, tex[/tags]