The majority of inner tubes will be made of butyl rubber. It’s the least expensive material and also the most robust. A butyl tube will be black and is repairable with a standard puncture kit if you get a flat.
Inner tube manufacturers often also have lighter weight butyl tubes in their line-ups. These are just made of thinner rubber. The weight saving comes at the expense of a bit more fragility though, so you need to be a bit more careful not to pinch a lightweight tube when fitting it. They are also likely to be more prone to punctures.
Latex inner tubes are lighter, roll faster but are fragile and leak air
Finally, there are latex tubes. These are the lightest option and also roll faster than butyl. But they are even more fragile than lightweight butyl tubes and harder to fit. And they leak air more quickly than a butyl tube, so you need to reinflate them before each ride. They can’t usually be repaired if they do get a flat either.