Bought Lenovo T420 without hard drive. Don't know which type of hard drive to buy?

I bought a laptop Lenovo T420. Its without harddrive. Can anyone tell me what type of hard drive will it support. Supplier says its SSD Sata. What is this mean?

Your T420 has multiple options.It should have a standard SATA drive(Either 2.5inch Sata Hard drive or Sata SSD 2.5inch) , but it also has an mSata socket as well ( takes mSata SSD which is like a slot in card).So it could have 2 drives, an SSD mSata CARD and a normal sized Sata drive.

It probably means you need to buy an SSD rather than an HDD, and you need it to be SATA rather than anything else.