I'm going to assume you know that humans, and all recognised life on earth is carbon based. This is because the outer electron shell of carbon has 4
electrons, allowing the maximum number of connections, 4. Atoms inherently try to get 8 electrons in their outer shell, as this is their most stable
form. Carbon is the lightest and smallest atom with these 4 electrons in it's outer shell. It's been theorized that silicon, the next lightest atom
with 4 electrons in it's outer shell, could support as many different combinations so as to be able to create life as well.
Most theories on the silicon lifeforms believe they would be slower to move, since unlike carbon, silicon's natural state is crystaline. So they
would probably be a lot slower, but this may not be the case. It's also speculated that we might not recognise a silicon life form as life at all,
because it would be so radically different than that of carbon based life.
If you watch Star Trek:TNG, the Crystalline Entity was an attempt of showing a silicon lifeform. Most xenobiologists agree that the most likely form
of silicon life out there would be that of some kind of crystal tree, which we would see and only think it was a natural formation. However, break a
piece off, and it's form of DNA would cause it to react a specific way, and possibly grow back.
Hope this helped a little