What is a macro ?

Macros are intellectual properties that you can  use in your design. You do not need to design it.
For example, memories, processor core, serdes, PLL etc.  A macro can be hard or soft macro.

Soft macro and Hard macro are categorized as IP.

Soft macros:

Soft macros are used in SOC implementations. Soft macros are synthesizble RTL form, are more flexible than hard macros in terms of reconfigurability. Soft macros are not specific to any manufacturing process and have the disadvantage of being unpredictable in terms of timing, area, performance, or power.  Soft macros carry greater IP protection risks because RTL source code is more portable and therefore, less easily protected than either a netlist or physical layout data. Soft macros are editable and can contain standard cells, hard macros, or other soft macros.


Hard macros:

Hard macros are targeted for specific IC manufacturing technology. They are block level designs which are optimized for power or area or timing and silicon tested. While accomplishing physical design it is possible to only access pins of  hard macros unlike soft macros which allow us to manipulate the RTL.  Hard macro is a block that is generated in a methodology other than place and route and is imported into physical design database as a GDS2 file.