There are plenty of elements that can penetrate or hold to the surface such as grout, dyes, resins, oil, water and etc. Many products on the market have been designed to beautify and protect the surfaces of stone, tile and grout, and sealer is one of them.
Sealers can be water-based or solvent-based. Take note: most water-based sealers cannot be used outside so you might want to consider that. As the name implies, it seals the surface tight against chemicals, water and other contaminants.
By applying sealer, you completely occupy the porous grout structure with a stable, hard grout sealer before the water moves in. This results in strengthening the tile and looking great. Sealing is done to create a protective barrier against spills and permanent stains. It also ensures that future tile and grout cleanings yield the best possible results.
It is important to realize that a sealer is not an impenetrable barrier – it only provides reaction time to deal with spills. Bad news is there is no really guarantees applicable to tile/sealing. Good news is sealers come with a life expectancy of up to 15 years depending on the quality of the tile, maintenance procedures and so forth.
For example, an unsealed floor can stain immediately, whereas if a floor is sealed it can resist the stains and can have a reaction time up to 4-5 hours. When it comes to finishing off your tile, a tile sealer may or may not be a good idea.
It is always a good idea to seal the tile grout, but depending what material your tile is made of, will determine whether or not you should seal it.
Some tiles will be damaged by certain tile sealer leaving them brittle, dark, or faded. So it is important which type of tile do you have and what kind of sealer does it matches.