What is a TPM2 "object context"?

The man page for tpm2_load has the following example: > To load an object you first must create an object under a primary object. So the first step is to create the primary object. > > tpm2_createprimary -c primary.ctx > > > Step 2 is to create an object under the primary object. > > tpm2_create -C primary.ctx -u key.pub -r key.priv What exactly is the primary.ctx file that is created by tpm2_createprimary and used by tpm2_create? The man page for tpm2_createprimary calls it the "object context": > -c, --key-context=FILE: > > The file path to save the object context of the generated primary object. And I can get some information about the file's contents with tpm2_print -t TPMS_CONTEXT primary.ctx:

version: 1
hierarchy: owner
handle: 0x80000000 (2147483648)
sequence: 128
contextBlob:
        size: 1506

But I still don't understand what I'm looking at. What is this "object context" file and why is it necessary?