The full meaning of TDMA is Time Division Multiple Access, while the full meaning of CDMA is Code Division Multiple Access. TDMA functions in such a way that it divides or chops the channel into portions of time sequentially. The TDMA channel users will have their own round-robin turns in transmitting and receiving data, respectively.
This simply means that only a user will be in use of the channel at any point in time. TDMA has started becoming out of use as it is being considered to be outdated technology. It has also been a part of GSM for quite a while now.
On the other hand, CDMA is a form of multiplexing that gives chance for a single transmission channel to be used by several signals. This simply signifies that multiple users can make use of the channel at the same time. Hence, various users can receive and transmit data simultaneously.