if  the lines are close together,do that mean that it's a sharp drop ? the intervils are  2 ft.

Depending on the scale, yes.

At 1"=100', the slope could be relatively mild

At 1"=20' then we're looking at a steeper slope.

Closer together lines represent steep inclines or declines. Further apart lines represent gradual inclines or declines. 

Count five lines and follow it around .That will be 10 foot . Pretty easy to  distinguish drop-offs from  flats .  Look for point , channels , humps...

Broken Bow Lake, Oklahoma, a real lesson in topography.

Thanks everyone