In Spore, you will meet many different creatures, but all creatures are part of a certain species.
Cell stage Species Edit
In the cell stage, you'll encounter cells. Some weak, others strong. Some species, such as Nosey, can give you good parts. There are six parts you can unlock. These parts are spike, jet, cilia, proboscis, poison, and electric. These are earned by killing cells of certain species that contain these parts. For more info, see completist.
Creature stage Species Edit
In the creature stage you will find creatures in an area called a nest. This is the creature's species. You can choose to befriend the species or kill them to extinction. There will be many species you encounter, some tougher then others. There will also be rogue creatures and epic creatures, which are way tougher than normal species.
Tribal stage Species Edit
In the tribal stage you will still see many creature species still, which you can kill for meat if you are a carnivore or an omnivore, or you can give them a bone if you want to domesticate them and get a pet to lay eggs for food and attack wild animals who attack your tribes babies. You will also see different tribes, which have a specific color as their name, such as pink or cyan. You can decide if you want them as an ally or if you want to kill them and cause their species to become extinct.
Civilization stage Species EditIn the civilization stage tribes will still be around, but all you can do with them is run over their members or destroy their main hut. Creatures will also still be around, but you can't do much with them either. You will also meet other civilizations. They will have creatures in them that look just like your creature, only they will have a different color. This color is their species. It's up to you to capture them religiously, with military force, or buy their city.
Space stage Species Edit
In the space stage, you will meet species of all the previous stages other than the cell stage. This time, however, you will meet different species that are part of empires. They will talk to you and you will talk to them. It's up to you to befriend them or kill them off.