Speed is scalar, velocity is vectorial in "easy" words speed is the quantity of distance units per time units
while velocity is speed plus a defined direction and sense
--------------------- MERGED ---------------------------
Example an object that is mooving at a speed of 7 kmh
can have an horizontal velocity of 5 km/h, a vertical velocity of 5km/h and a Z velocity of 0 km/h (By Z i mean the 3rd axis of a 3d space)
EDIT: I didn't made the calculation for units, so the units I gave migth be wrong scince i made it in my head and it is just an example xD