It literally means "about" or "concerning".
Here are some examples:
* Tungkol saan ang usapan ninyo? (What are you talking about?)
* Mayroon akong sasabihin tungkol sa proyekto. (I have something to say regarding the project.)
* Tungkol sa iyong kahilingan, pakitingnan mo ang impormasyong ito. (Regarding your request, please check this information.)
You can also use patungkol sa which means "with regard to". It's often used in more formal contexts.
* Patungkol sa iyong sulat, nais kong linawin ang ilang bagay. (With regard to your letter, I would like to clarify a few things.)
* Patungkol sa pagpupulong, narito ang agenda. (With regard to the meeting, here is the agenda.)
Remember that the choice of word depends on the context and desired level of formality.