OK, I'm going to have to nerd it up a bit here and then explain each
Waveheight is the total height of the wave, meaning from the top of the crest (highest point of the wave) to the base of the trough (bottom of the wave). Pleae note that waveheight is NOT how much higher the wave gets above were the water would lay if it was dead calm. Example. A 3ft wave is 3ft crest to trough but that also means its only 1.5ft higher than were the water would normally be on a calm day.
Period is the total distance between the crests (distance from the top of this wave to the next one in line). This is something to watch. If the period is very low then the waves are closer together meaning they hit you quicker and are harder to handle the boat in. You can be in 3 foot waves but the period is 15 feet because last night there was a storm blowing through and the lake is calming down and these are rolling waves. Another thing to watch is a sudden shift in wind direction. You can have a 20 km/hr west wind switch to a 20 km/hr N wind and this adds to the frustration of steering a boat and maintaing speed because the waves will be hitting you from different directions.
found another great site called windyty.com, its free, you can choose to look ahead of wind changes and colour deems windspeeds.
As stated 1 meter is approximately 3 feet
1 Knot = 1.15 mph= 1.852 kph
1 mph = 0.87 knots = 1.6 kph
1 kph = 0.54 knots = 0.62 mph