Force is everywhere. It is similar to oxygen. As we breath air, we supply our lungs with oxygen in order for them to function. Everything in our body needs oxygen because it gives life to us.
It is the same for our Force Core.
If oxygen is around us, so does energy as well. As we accumulate the energies surrounding us, they become converted to Force. These energy supplies our core, making it function to use as well.
Force can be used by everyone, whether they are zolgarians or Guardians. Anyone can use Force as long as one has Force Core to hold the amount of energy and to convert it into Force. Without a core, one cannot accumulate energy. And if one cannot have energy, they cannot have Force as well.
There are two types of Force users: Warriors who loves to fight in close-quarter combat, and Snipers who loves to fight from long distances. But a Guardian can also be both, having an advantage against two types of Force users.
A Warrior is a Force user who imbues Force around themselves, a common skill called BodyEnhancement. It is a skill where one coats themselves with Force to either protect them or to increase their strength in close combat. Silvera, Teresia, and I fall into this category.
A Sniper is a Force user who uses Force from long distances. In order to do this, they have to manipulate the energy around them without vacuuming them into their core. Meaning, they have to convert the energy into their Force without putting them towards their Force Core. Once they have done this, a Sniper can now use the Force in the air as their weapon to hurl towards their opponents. Rain falls into this category.
However, being a Sniper consumes more Force than being a Warrior. While a Warrior can use any amount of Force to imbue to themselves, a Sniper has to use a tremendous amount of Force in order to convert the energy in the air to their own without the need of pulling them to their core.