The U.S. Navy is again modifying the designations it assigns to its various types of ships in order to keep up with changing technology. The new changes reassign several types of transports, some of them novel new designs, to designations that begin with “E” (for Expeditionary). Thus ships that play a crucial role during overseas interventions (during war or peace) now have type designations that begin with E. Using these designations has been going on for over a century but were not codified until 1920.
Current designations include CGs for Cruisers (the "G" stands for guided missiles, which all major warships use these days.) CVs are aircraft carriers (an "N" means nuclear powered.) DDGs are destroyers. FFG are frigates. LHA, LHD, and LPD are large amphibious ships that usually carry a battalion of marines, plus helicopters and landing craft. LSDs are smaller amphibs, and carry only about half a battalion. MCM and MHC are mine clearing ships. PC are coastal patrol boats. SSBN are nuclear powered ballistic missile submarines, SSN are attack subs. LCS are Littoral Combat Ships (recently reassigned to frigate type) and AKE are combat transports.
The new E designation renames JHSV (Joint High Speed Vessels) as EPF (Expeditionary Fast Transport). MLP (Mobile Landing Platforms) become ESD (Expeditionary Transfer Docks). AFSB (Afloat Forward Staging Bases, these were formerly T-MLP) become ESB (Expeditionary Base Mobile.) All these are relatively new ship designs.
The JHSV (now EPF) was developed, after 2000, from catamaran type high speed commercial ferries. They have proved themselves and the navy is buying more of them.
MLP (now ESD) is a new design developed in the last decade. The U.S. Navy received the first one in 2013. ESD looks like a container ship with the main deck lowered to approximately the height of a dock. On the side of the ESD are mooring fenders so cargo ships can, literally, tie up like at a dock. The ESD also has ramps for getting cargo from ships or a dock. Cargo would be transferred to landing craft or LCAC (air-cushion high speed landing craft which can carry 60 tons of cargo). The ESD can also partially submerge itself so that its deck is underwater. Landing craft can then move over the deck and the ESD can bring its deck back out of the water so the landing craft can be loaded. Currently ESDs are to each carry three LCACs.
The AFSB (now ESB) is an ESD variant that can also carry helicopters and MV-22 tilt rotor aircraft. The navy plans to increase the fire resistance of part of the deck so that the ESBs can also handle vertical takeoff version of the F-35.