Silicone is mostly used for 3D découpage where the amount used can be varied to allow some areas to be raised more than others which gives you more control than the uniformity of sticky fixer pads do. Silicone is also useful to infill the back of embossed items where crushing may be an issue. It can also be used for regular gluing but it does take a long time to dry. It starts as a milky clear colour and dries a bit clearer though not completely.