The inner cases are for inside. The outer cases are for being on a surface or at an open place — and they answer the same three questions:

Question	Ending	tori (market square)	pöytä (table)
Missä? — where?	-lla / -llä	torilla — at the market	pöydällä — on the table
Mistä? — where from?	-lta / -ltä	torilta — from the market	pöydältä — off the table
Mihin? — where to?	-lle	torille — to the market	pöydälle — onto the table

Put the two sets together and you have the whole grid of six local cases:

	where?	from where?	to where?
inner	-ssa / -ssä	-sta / -stä	-Vn
outer	-lla / -llä	-lta / -ltä	-lle