Nathan, I will try not to be to wordy here but here is a snap-shot on sealers.
There are three basic types of sealers for stone and grout.
1, Penetrating sealers, generaly sylicon either water or solvent based. These sealers penetrate the stone or grout and become part of the product. You cannot see them on the surface and they help prevent staining. Used on all types of stone, Marble, Slate, Sandstone, Granite and the grout for all. They are desireable if you do not want to change the appearance of the surface and should be applied every 1 to 2 yrs as a rule.
2, Topical sealers, generaly acrylic or polymer and water based. They act much as floor finish would and enhance the gloss of the surface while preventing most staining. They are generaly affected by urine, amonia, alchol, ect. The downside to these is they will have to be reapplied and/or stripped and reapplied on a regular basis.
3, Permanent type sealers, These are generaly solvent based urathane type products. Althoughly rarely seen, Run don't walk away. Very difficult to remove if peeling or damaged and rusult in Hazard waste disposal amoung other problems.
If you would like any more info, contact me.