Mortars and pestles are a bowl/club combination used to crush, mash, grind or pound various types of food. They can be made of lots of different materials and in a variety of shapes. Although there are mortars and pestles made of wood, they tend to be made of heavier materials, such as brass, stone, granite, ceramic materials and marble. I have three brass sets and one made from volcanic stone. I use them for mashing avocados and other ingredients for guacamole. I also use them to grind spices that originally come in seeds, like cumin and fennel.
If you don't have a mortar & pestle, you can use a coffee bean grinder to grind spices.