These are characteristics of the various spanning tree protocols. The italicized words indicate whether the particular spanning tree protocol is Cisco-proprietary or an IEEE standard implementation:

The default spanning tree mode for Cisco Catalyst switches is PVST+, which is enabled on all ports. PVST+ has much slower convergence after a topology change than Rapid PVST+.

Note: It is important to distinguish between the legacy IEEE 802.1D-1998 (and earlier) standard and the IEEE 802.1D-2004 standard. IEEE 802.1D-2004 incorporates RSTP functionality, while IEEE 802.1D-1998 refers to the original implementation of the spanning tree algorithm. Newer Cisco switches running newer versions of the IOS, such as Catalyst 2960 switches with IOS 15.0, run PVST+ by default, but incorporate many of the specifications of IEEE 802.1D-1998 in this mode (such as alternate ports in place of the former non-designated ports); but to run rapid spanning tree on such a switch it still must be explicitly configured for rapid spanning tree mode.