You can use a traditional blender for soups but a stick blender will make life so much easier for you. Some manufacturers call this an immersion blender because the head of the blender is immersed in whatever you wish to blend. The one caution is to wait for hot recipes, such as soup, to cool a bit before blending.
Place the bottom of the blender against the bottom of the pot or bowl. This actually forms a slight suction and foods will tend to splash less. If I know I am going to use my stick blender, I try to use a pot or bowl with higher sides to reduce any spatter.
This is one of my favorite kitchen tools. The one I have has a lot of attachments, and while the important one is the blender itself, I do use the mini food processor attachment that came with mine almost as much as the blender itself. It is perfect for dressings and spreads, such as pesto, where clean up of a food processor or blender would be a hassle.