Summoning a spirit, demon, or any being is the act of ordering or demanding it's presence to you. It is one projecting their will with intense force to bring the being from it's present location and traverse it through time and space to where the caster demands. Many practitioners' feel that the act of summoning is negative and also feel that it is disrespectful to the being and to magic The act of summoning a spirit or being does not mean that the caster will have any control over the beings actions, because summoning by itself is just the act of bringing the being to you.
As far as interacting with the being is concerned, it takes great will, focus, and responsibility alone just to keep the being in your presence and to communicate with it. Controlling a spirit or being on the other hand is not something that can easily be done despite many people's belief otherwise. It is funny that people speak so lightly and candidly about the act of controlling spirits, demons, and other beings; considering the fact that these beings are usually more powerful for a lack of a better term than us humans. Spirits and other such beings exist beyond our physical realm, they dwell within various realms of the astral and spiritual planes.
Any act of desire or will, in which one projects their will into the cosmos to bring about a specific change or to manifest one's will and desire's is an act of magic. This includes smaller things such as simple prayers, wishes, and spells which in my opinion are just a more glorified but stylish form of a prayer; to things such as ritual, ceremonial, and deeper forms of magic.
When working with spirits or any being, or any act of magic for that matter, one should know that regardless of your will or desire, the desire or will of the cosmos is greater, and should the desire and or will of the cosmos oppose or disagree with your own, you will have difficulty succeeding.
In addition to summoning spirits and beings, there is also the act of invoking and evoking. The act of invoking is requesting the essence of a spirit or being to come within you. It can be seen as unifying your spirit with theirs thus depending on your goals, intentions, and purposes will add to the strength and magic that you are trying to cast. The act of evocation is request the presence of a spirit or being to come before you. This can be done in many different manners from simple prayers, spells, making offerings that appease the spirit or being etc. Thus invoking is calling a being within and evoking is calling a being from without. An example of these acts can be found within various ritual aspects of Wiccan coven rituals in which the high priestess and the high priestess either invoke or evoke the Goddess and God.