You will not have to seal your tiles if they are glazed ceramic or porcelain. However, if you have unglazed tiles such as terracotta or natural stone you will have to seal them. You might have to use a different type of sealer to seal unglazed tiles but there are many multi-purpose stone and grout sealers available on the market. Keep in mind that you could potentially stain your unglazed tiles with grout sealer, and it is very difficult to remove after the fact.