Immersion is sense of being surrounded by the virtual environment. There are different levels of Immersion. Virtual Reality Head-mounted Displays can create immersion up to a degree. As technology improve, we can expect increasingly immersive experiences.
Presence is different from Immersion. The former means that you feel you are within the virtual world while the latter means that you are merely surrounded by the virtual world. In VR, Immersion is easier to achieve than Presence. While modern HMDs can create an immersive VR experience, Presence is a bit more elusive.