Tankettes were a type of lightly armed and armored tracked combat vehicle resembling a small tank that was mainly intended for light infantry support or reconnaissance.
Typical examples of the period were the Carden Lloyd models were perhaps the best examples
http://en.wikipedia.org/wiki/Carden_Loyd_tanket... They indirectly led to the development of the Universal Carrier which was perhaps the most successful military use of a tankette (although it's more often referred to as an armoured personnel carrier i believe.
Following the war, tankettes have been largely abandoned, although the concept has sort of survived in light and recon vehicles such as the US M50 Ontos (50's & 60's), the British FV101 Scorpion 19070's onwards) and recently in vehicles like the German Wiesel ...
http://www.army-guide.com/eng/product943.html 