What are the lettered and numbered signs next to airport runways and taxiways?
From left to right in your image


  16 CAT II / III


Refers to the runway number, and also the ILS Category that particular runway supports. However that is just secondary information. The primary purpose and position of this sign is actually to indicate the hold-short position for the numbered runway.


  E6 34/16


Refers to the taxiway designation (E6) and the runway(s) it leads to (34/16 being the same runway 34 one way and 16 the other)


  {Unreadable} and E6 L→ 10→


Both of these signs are the same, one is pretty much unreadable the other is again on taxiway E6 and points that Taxiway Lima (L) is to the right as is runway 10.



Pilots are unable to see these signs on landing, signs like this on taxiways are almost exclusively for ground operations - not just the aircraft but the variety of vehicles that operate on the apron of an airfield.



These signs are equally not useful at the point of takeoff, none of the information presented on them is relevant for that phase of operation.



Pilots will have a "map" of an airfield with them which will indicate the same information as presented on these signs. Ground controllers will typically mention which taxiways to use when guiding aircraft (and other vehicles) using the apron and taxiways. For example, at the airfield pictured the ground controllers may have instructed the pilot that they were cleared to "hold short of Runway 10 via Taxiway Echo 6" or may have told a landing aircraft that they should "clear the active runway at Taxiway Lima".

Here is a graphic that many websites use a variation of:


Source: americanflyers.net