Hover Vessel (HV)
A Hover Vessel is a type of hover craft. It is only useable on the surface of a planet. To build one you need a Hover Vessel Starter (previously called a Ground Vessel Starter), which is made by combining a Core, a Hover Engine and 8 Hull Blocks in the Large Constructor.
Small Vessel (SV)
A Small Vessel is a flying vessel that can fly around within the atmosphere of a planet as well as enter space but can't enter another sector. To build one you need a Small Vessel Starter, which is made by combining a Core and 8 Hull Blocks in the Large Constructor.
Capital Vessel (CV)
In order for a Capital Vessel to be fully operational it requires a Generator, a Fuel tank (Small or Large), a RCS, a Cockpit, some Thrusters, and a Gravity Generator. To quickly get to other planets in the solar system, you can add a warp drive to a Capital Vessel.
A capital vessel must be constructed in space and can enter the atmosphere of any planets as of update 5.0.
A Base is not a vehicle, but instead a structure. The base is similar to your Capital Vessel, except that it cannot move and is for planetside operations. To build one you need a Base Starter, which is made by combining a Core and 8 Hull Blocks in either a Small Constructor, or Large Constructor.
In order for a Base to be fully operational it requires a Generator, and a Fuel tank (Small or Large). The fuel tanks also require Fuel Packs. (Refer to Fuel Tanks). Once powered, a base can contain a multitude of different tools, provide you with safety, and support you while on the planet's surface.