Memory Partitioning- means partitioning the memory into small units or blocks & load the data or code into the blocks, & use this data & code when required by a process.
Paging- is a techique to manage the memory in the form of equal soze of blocks called pages. Only those pages which are having the data, required by a process, will be loaded to memory not the entire file. This allow the OS to execute even very large processe which requires more memory that your system can't load the entire process at once.
Segmentation- is a technique of memory menagement, mainly introduces for memory protection, where memory is devided into variable size of chunks called segments.