So the heading says it all. Docs describe wallet AssuranceLevel param as “Desired assurance level based on the number of confirmations counter of each transaction.” So what does this mean in layman’s terms?
It’s a number of blocks that happened on the same branch after your transaction were included in the blockchain. The difference is basically whether to wait for 9 or for 15 blocks to show the green badge that transaction is “high” level of assurance.
P.S. I reckon “strict” should be used only for exceptional cases of extreme paranoia 
I see, thanks again! 