What does it mean if an organism is more adapted to its environment?

the more adapted to the environment a species is means they are more suited to reproduce and survive in their habitat

If an organism is more adapted to its environment, it suggests that this individual possesses a greater amount of advantageous alleles. This will resultantantly influence its phenotype, meaning these organisms have physical characteristics (whether internal or external) that provide it with a greater likelihood of survival. For example, a mammal with the alleles for fur as opposed to no fur, would be more adapted to a cold environment, as they will be able to retain their warmth. Furthermore, this means that they have a lower metabolic expendature, therefore providing them with relatively more energy for other functions for survival such as reproduction or feeding (hence survival of the fittest). In summary, advantageous alleles deem an organism more adapted to an environment, through the greater likelihood of successful reproduction to occur. At higher levels, this concept is termed Biological Fitness.

It means that it has features that enable it to survive better, eg. camouflaged to its surroundings. These initially arise from random mutations in the DNA - if a mutation gives the organism a trait that is beneficial, the organism is more likely to survive and pass on its genes.