Do I have an SSD and a hard drive on my MacBook Pro? I looked at the details provided in  my
system report/storage and I noticed that it appears I have a hard drive of 499.05GB and an additional SSD drive of 499.42GB. Does this mean I have 1TB of data? I only have 139GB available so do I have 500GB 'hiding' somewhere? (If so where??) 
I am unsure how to interpret this information- why does it list both storage types? Is it duplicating the information?


  Macintosh HD:
  
  Available:    139.8 GB (139,800,666,112 bytes)
  Capacity: 499.05 GB (499,046,809,600 bytes)
  Mount Point:  /
  File System:  Journaled HFS+
  Writable: Yes
  Ignore Ownership: No
  BSD Name: disk1
  Volume UUID:  EF0908C8-XXXX-XXXX-XXXX-XXXX80333709   
  
  Logical Volume:  Revertible:  Yes (unlock and decryption required)
  Encrypted:    Yes
  Encryption Type:  AES-XTS
  Locked:   No
  LV UUID:  8CC9C88D-XXXX-XXXX-XXXX-XXXX2002329B  
  
  Logical Volume Group:
  Name:    Macintosh HD   Size:    499.42 GB (499,418,034,176 bytes)
  Free Space:  18.9 MB (18,903,040 bytes)
   LVG  UUID: EE040070-XXXX-XXXX-XXXX-XXXXA83B309   
  
  Physical Volumes:
  
  disk0s2:     #is this a second disk?
  
  Device Name:  APPLE SSD SM0512G
  Media Name: APPLE SSD  SM0512G
  Media   Size:   499.42 GB (499,418,034,176 bytes)
  Medium Type:  SSD
   Protocol:  PCI
   Internal:  Yes
  Partition Map Type: GPT(GUID Partition Table)  #does this mean its partitioned?
  Status: Online
  S.M.A.R.T. Status:  Verified
  PV UUID:    A1391405-XXXX-XXXX-XXXX-XXX2E8FCDF3
If you consider SSDs being hard drives then you have an SSD and a hard drive on your MBP. It's still only one device with ~500 GB disk space.

The main partition of your SSD is encrypted with FileVault2. While enabling FV2 the main partition is transformed to CoreStorage which is an LVM - an additional layer between physical disk and file system. The resulting Logical Volume is shown as an additional disk in Disk Utility/diskutil info.

A common partition layout looks like this:

disk0 (500.1 GB) → disk0s1 (209.7 MB) EFI
                 ↘︎ disk0s2 (499.4 GB) Macintosh HD
                 ↘︎ disk0s3 (650.0 MB) Recovery HD


disk0s2 (Macintosh HD) is mounted to root (/)

After converting the disk to CoreStorage, disk0s2 is converted to a Physical Volume which sets up a Logical Volume Group. The existing file system on disk0s2 is shrunk a bit, converted to a Logical Volume and encrypted:

disk0 (500.1 GB) → disk0s1 (209.7 MB) EFI
                 ↘︎ disk0s2 (499.4 GB) LVG/PV → disk1    (499.05 GB) LV/Macintosh HD
                                             ↘︎ metadata (~370 MB)
                 ↘︎ disk0s3 (650.0 MB) Recovery HD


Now disk1 (~disk0s2) is mounted to root (/).

So disk1 is almost congruent to disk0s2 (except some 100 MB at the end of disk0s2 which is used for metadata and isn't encrypted).



CoreStorage is not limited to encrypt volumes as FileVault2 "container". Every regular volume can be converted to a CS LVG/PV/LV. Apple uses it to create Fusion Drives and SSDs are usually partitioned/formatted as CoreStorage volumes.