An amoeba uses its pseudopods (fake feet, literally translated) to extend out from its cell body to engulf foreign bacteria. It then breaks the cell membrane off of the outside, forming a membrane around the bacterial cell (or other foreign body) that is now inside the amoeba cell. It can then inject enzymes to digest the bacterial cell and break it down to use for energy. In essence, it eats the bacteria. A good example of this is your lymphocytes (or white blood cells) engulfing foreign bacteria or infected cells as part of your immune response to infection.
