They tell what size can be stored in a integer variable. To remember the size you can think in terms of :-) 2 beers (2 bytes), 4 beers (4 bytes) or 8 beers (8 bytes). Int16:- 2 beers/bytes = 16 bit = 2^16 = 65536 = 65536/2 = -32768 to 32767. Int32:- 4 beers/bytes = 32 bit = 2^32 = 4294967296 = 4294967296/2 = -2147483648 to 2147483647 More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.