YELLOW-JACKET WASP

I think " yellow-jacket " wasp is a generic term for most wasps.  This one isnt our real pesky one ( I dont think) its a lot smaller than the german wasp and is only about as big as my small finger-nail.  Its a pretty wee thing - some wasps are very handy at killing some insect pests perhaps someone could enlighten me about this one. ?
rgds poo