Hey, when I look at websites, how do I know if a bit is made for metal, wood or plastic?
Companies that make wood router bits typically do not make metal cutting end mills, and vice versa.
But both may make bits for plastics. And there are also bits for different kinds of plastics. Softer plastics and harder plastics need different cutter geometry for optimum results.
Generally, if they are being called endmills, then they're most likely metal cutting bits. If they are called router bits, then they are for wood. If they are for plastics, the description should tell you that.
There are also router bits made for non ferrous metals, like aluminum and brass. Non ferrous router bits are similar to plastic cutting router bits.
Generally, you can use router bits to cut wood, plastics, and non ferrous metals. Sharp bits will give good quality cuts in any of these materials.
What you don't want to do, is use a bit that's been cutting wood to cut plastic or aluminum. Keep bits for plastic and aluminum separate, and never cut wood with them. Wood is actually very abrasive, and will dull bits faster than plastic and aluminum.