Introducing ProcessWire ProFields: Table – it lets you literally define your own Fieldtype! This is one of the most exciting ProFields and it's something very different than any other Fieldtypes. I think it is best described by this screencast (be sure your sound is on):
Special thanks to Joss for his great voiceover on this screencast. Please view the video at 720p and full screen if possible.
Read more about the Table Field
Table is part of the ProcessWire ProFields package now ava
Use this for tabular data, like rate tables or other things that you might typically represent in a spreadsheet. Use it for situations where you don't need the full-blown flexibility of repeaters, as it's technically more efficient with far less overhead than repeaters. Something like the Events Fieldtype could be very easily re-created via a Table field, but the potential uses are far broader. But for the most part, think tabular data when it comes to the Table field.