An ecosystem is a biological community of interacting organisms and their environment. Some examples include: rainforest, tundra, desert, freshwater, and it goes on. Abiotic factors are the non living components of the ecosystem such as water, wind, sunlight, atmosphere, temperature, and so on. On the other hand the biotic factors are animals, plants, bacteria, fungus, etc. When you combine both of these factors you get an ecosystem since it covers all aspects of what makes a specific ecosystem one way or another.
(An example would be the desert:
Abiotic factors would be: hot temperatures, little water, etc.
Biotic factors would be: camels, fennec fox(animals), cacti(plants),)
I hope this helps :D I’m sorry if it was multiple choice or anything :(