for information on the chromosome in biology, see Chromosome
In genetic algorithms, a chromosome (also sometimes called a genome) is a set of parameters which define a proposed solution to the problem that the genetic algorithm is trying to solve. The chromosome is often represented as a simple string, although a wide variety of other data structures are also in use as chromosomes.
A genetic algorithm creates many chromosomes, either randomly or by design, as an initial population. These chromosomes are each evaluated by the fitness function, which ranks them according to how good their solution is. The chromosomes which produced the best solutions, relatively speaking within the population, are allowed to breed, called crossover. The best chromosomes' data is mixed, hopefully producing a better next generation.