Glue dots can be temporary, permanent, and super-strength.
Temporary glue dots are useful for sticking posters on a wall surface that will at some point be removed and when it comes to using temporary glue dots as a scrapbook adhesive, they are just perfect for holding things in place on your page while you're still experimenting with your arrangements. Many people choose to use a temporary glue dot to adhere to their photographs so that it can be repositioned if they accidentally stick it down slightly crooked. You can also swap the photograph out at a later date when using a temporary glue dot.
Permanent glue dots are great for when you're 100% happy with your scrapbooking layout and are ready to finish it off. I nearly always use permanent glue dots, particularly when making embellishments for my scrapbooking pages.
Super strength adhesive dots are not really necessary in scrapbooking adhesives as usually, you aren't trying to adhere something together that is particularly stubborn. Though it's great for wood or metallic embellishments, super strength dots are more suited to projects around the home such as holding a picture frame in place.
Glue dots can be fairly decent sized, like the size of a fingerprint, down to really quite small, like the micro glue dots in the photograph below. Teeny tiny adhesive dots are great for creating fiddly embellishments and sticking little fiddly things onto your page like small plastic gems or flowers.