What is the difference between .LIB and .OBJ files? (Visual Studio C++)

I know .OBJ is the result of compiling a unit of compilation and .LIB is a static library that can be created from several .OBJ, but this difference seems to be only in the number of units of compilation. Is there any other difference? Is it the same or different file format?I know .OBJ is the result of compiling a unit o