A general fertiliser is one which is balanced in nutrients. When you look on the back of a fertiliser packet, you'll see these letters, followed by some numbers: NPK
N = Nitrogen (for leaves)
P = Potash (for flowering/fruiting)
K = Potassium (for roots)
If the numbers after the NPK are broadly equal, it's a general purpose balanced fertiliser. This could be fish blood & bone (FBB, sometimes written in a different sequence e.g. BFB) or Growmore, for exampe.
Or a more specific fertiliser would have a higher number for one of the letters.