Differences of Internal and External fragmentation:
External fragmentation: Memory allocation is dynamic, Segments are of variable size. When all blocks of free memory are too small to accommodate a segment.
Internal fragmentation: Memory is allocated in static as fixed-sized unit (page frames), when the request is smaller than page size or can not be evenly divided by page size, at least part of one page (the last page) won't be used by the requester and unavailable for use by others.
Internal fragmentation: These phenomena in which there is wasted space internal to a partition due to the fact that the block of data loaded is smaller the partition.
External fragmentation: these phenomena in which there are a lot of small holes in memory. As time goes on, memory becomes more and more fragmented, and memory utilization declines.