WAVELENGTH - is the distance (units of length: meters) between the successive top most points in the snap shot of the wave at a time instant.
It is the distance between two particles in the medium, or two points in the wave - which are in the same phase.
When u see ripples in water - ups and downs - it is the distance between consecutive ups or downs.
Frequency - the number of times the particles oscillate up and down in one second. For example, if some particles or leaves or paper piece is floating on water and the water has ripples, : the number of times the leaves go up and down in one second tells the frequency.