diffrence between C4 plants and and CAM plants?

Answer 1

C4 and CAM plants both use PEP carboxylase to fix (i.e., incorporate CO2) carbon initially before using RUBISCO. Most other plants (i.e., C3 plants) use RUBISCO directly. In the case of C4 plants there is a spatial separation of PEP carboxylase (mesophyll) and RUBISCO (bundle sheath cells). In the case of CAM plants there is a temporal separation between PEP carboxylase activity (night) and RUBISCO activity (day).

Answer 2

They both have a way of condensind carbon (in the form of carboxilic acids) around the carbon fixing enzyme (Rubisco) to avoid it oxigenase activity, hence enhancing the water efficiency of the plant (more photosinthesis while loosing less water)
The difference is C4 plants have a spatial compartmentation: They have the Rubisco around the central veins and they transport the acids to this zone of the leaf, so oxigen is far from rubisco at the time of fixing.
In CAM, the compartmentation is temporal: They open the stomata at night, to loose the minimum amount of water, and acumulate the carboxilic acids, and during the day, with stomata closed, they can use light to perform photointhesis using the acids acumulated during the night.