1. Evolution Strategies
Originally developed in Germany in the early 60s with Rechenberg and Schwefel being the main contributors. Main ideas include:
floating point representation with standard derivation: (x,) where x is a vector in n-dimensional space and  is the standard derivation that influeces how solutions are changed: x’= x + N(0, ).
mutation is the sole operator.
in most approaches  is changed dynamically (e.g. using Rechenberg’s 1/5 Rule).
employs a two-member evolution strategy.
Was later generalized to support multi-membered evolution strategies:
employs: uniform crossover and averaging crossover.
each member of the population has the same chance to reproduce (selection doesn’t consider fitness).
weakest individual is eliminated to keep a constant population size.

2. -ES and -ESs.
developed by H.P. Schwefel: 2-member population ((1+1)-ES) is generalized to multi-membered populations. 2 approaches are supported
()-ES:
 individuals produceoffsprings
the population consisting ofindividuals (the old generation and the parents) is reduced to  using selection.
relies on replacement
()-ESs:
lifetime of individuals is limited to one generation.
 individual produce  offsprings ( > ) with the best  surviving.
generates the new generation from the scratch
Moreover, the standard deviation undergoes evolution.

3. Evolutionsstrategie and GAs
Differences ES and trad. GAs :
real-code (ES) vs. binary string representation (GA)
selection is performed implicitly by removing unfit individual deterministically (ES); GAs employ a stoachastic selection process, and does not rely on removal..
selection after recombination (ES); selection before recombination (GA).
different handling of constraints: ES supports un-equalities as a part of the problem specification, and disqualifies illegal offspring; moreover, ES adjusts control parameters if illegal offspring occur too frequently. GAs, on the other hand, employ penalty functions.
mutation is less important for traditional GAs; crossover is less important for ESs.
Some scientists, e.g. Fogel, claim that ES and GAs are not fundamentally different (see also Hoffmeister’s paper [141]).