Different types of filler!
There are so many types of fillers... where do I start! Lets just start with the differences between some of the more popular fillers.
The fillers with bigger molecules are less likely to move or degrade, they tend to take on a little more water, and are better for areas in need of big volume replacement (such as your cheek bones). Examples of the heavier fillers would be: Juvederm Voluma XC, Radiesse, Restylane Lift and L, Bellafill and Sculptra.
The smaller, more refined fillers that are less likely to swell are better for fine lines and wrinkles. Examples of the more delicate fillers include: Restylane Silk, Belotero Balance, and Juvederm Ultra and Ultra Plus XC.
Most brands have multiple different products to meet your needs.
Other differences to note:
Longevity: non permanent fillers last between 6 months up to 2 years. The fillers with the bigger lift (cheek bones) last longer than the fillers used for more delicate lift (lips and fine lines).
Reversibility: If results are not desirable and you want your filler removed, all of the hyaluronic acids can be reversed with an injection of another medication (hyaluronidase). All of the others will require time for your body to reabsorb the material or excision is required (in the case of the permanent fillers).
In summary: providers will have their own preferences for which fillers they use based on their experience and comfort level with the filler. As long as they have experience with the filler you are receiving you should have a good outcome. For first time fillers, I would recommend a Hyaluronic acid filler to ensure you like the results before going for a longer term filler.
I hope this sheds some light onto the fog that lies over all the different fillers out there.