Photographical format known as CR2 is used by company named Canon. Canon itself created and upgraded it, it is derived from RAW format, but unlike RAW format, company called Canon has its own version or if you want its second own version. The main advantage is high quality photos that aren´t edited or there isn´t used any filter. To edit these files there are external programs for users. We can see bud compression ratio due to its high quality.
CR2 file format is based on CRW format, because it is its successor. CRW was original file format by Canon, which was released in 1997. During its life, it got many updates and on Februrary 1998 was released its latest version. Between programs that can open these files belongs Adobe Photoshop. Then there is Able Rawer, which allows to edit and control RAW files created in this file format.
To open these files you can use program written above that is called Able Rawer, which is for free.