- * Only in an THREADED_RTS build will there be multiple capabilities,
- * in the non-threaded builds there is one global capability, namely
+ * A Capability holds all the state an OS thread/task needs to run
+ * Haskell code: its STG registers, a pointer to its TSO, a nursery
+ * etc. During STG execution, a pointer to the Capabilitity is kept in
+ * a register (BaseReg).
+ *
+ * Only in a THREADED_RTS build will there be multiple capabilities,
+ * in the non-threaded RTS there is one global capability, called