Question about textures

Hi to everyone, sorry for this beginner’s question, but when i import an .OBJ or FBX file into Sketchup, which are the rules to keep also the textures? i mean, the textures have to be only in a type of file (like .TIFF or .TGA)? there should be a .MTL file (which i’m not sure what is it), the textures need to be in the same folder or into another? etc.
Thank you and happy new year!

SketchUp natively does not import FBX or OBJ. You could get an add-on, such as Skimp, to be able to import those.

If your other 3D program can export Collada, that should be a safe bet for bringing in materials as well.