Can someone help me sort out these terms:
Time and Sales - Level I - Level II - tick data

To me, it all seems the same, ie, number of contracts traded at x price level at the bid or the ask.

I am a bit confused about the difference between each term.

some definition here
Level 1 Definition

I added some wiki terms: tick, tick size, tick value, Time and Sales, Level 1 market data, Level 2 market data. etc..

You might want to look into Level 3 as well. it has been out for quite some time, yet very hard to find.