Ladder Diagrams -
Ladder diagrams are also called line diagrams or elementary diagrams.Ladder diagrams are used to represent the function of the control control circuit and associated devices but they dont show the components of the control circuit and their actual physical positions.As control circuit becomes more complex a ladder diagram can be less complicated to read than a wiring or connection diagram.
Connection diagrams or wiring diagrams shows the components of the control circuit in a resemblance of their actual physical location.
For creating and representation a program a Ladder logic programming language is used via ladder diagrams that relies on circuit diagrams. It is mainly used for creating programs or software for Programmable Logic Controllers (PLCs), used for industrial applications.
Initially the language evolved with being a technique for documenting the construction and design of relay racks in producing and processing control with each relay rack given with a symbol on the ladder diagram that is device connected under them with vertical rails. You will find a rung in a ladder look alike called as relay symbols.