wrapper is a package which is used to convert one interface to another interface or convert one data format to another format, etc. For example, if you have an IP using AMBA bus interface, but your design does not use it, then you need an AMBA wrapper to change it to your actual bus interface to integrate your IP
sometimes u need to write some interface to the tools in perl or tcl to customize the asic design tools to your requirement, these interfaces over the tools are called wrappers
in my opinion, warpper is, if we have a AXI interface, but i don't want all AXI transfer are to AXI INTERCONNECTION, and some of AXI transfer should go to another bus depending address, so i need design a wrapper to seperate AXI transfer to different destination.
sometimes u need to write some interface to the tools in perl or tcl to customize the asic design tools to your requirement, these interfaces over the tools are called wrappers