'Spot' colours are specific Pantone® Colours (e.g. TYGA orange is Pantone® 021).

'Process' refers to the 4 colour process that 'Litho' printers use to print full colour jobs (ie with full colour photos etc).

If your job requires full colour photos, but you want to print your logo in a solid spot colour, then you would need to choose 5 colour (process + 1 spot)