Islam is a religion covering all aspects of life: how to pray God, how to behave and control your own pulsions, how to marry properly according to God's law, how to split inherence, how to behave in war, etc.
Muslims believes indeed that God has sent the Torah and the Gospel. However, we also believe that humans have altered the original message of God to add inventions. However, we believe that Torah and Gospel as originally sent by God are similar to the current Quran.
For a Muslim, God is an entity which cannot represented by the human brain and any representation of God would be false (this is the reason we do not picture God). God is the creator of this Universe, he is One and Incomparable, is Merciful and Omniscient with knowledge of all things, including thoughts and feelings. I know that for many atheists, God is a kind of old man in the sky. This is absolutely false in Islam.
Islam is a decentralised religion. There is no authority representing the "muslim" world such as a Church. There is no confession and all prayers are directly made to God (you do not need to ask anything to anybody to talk to God).
Islam teachings are basically: say there is only one God and that Muhammed is his messenger. Do your five prayers per day. Pay the "zakat" (charity) for the poors. Do the hajj in Mecca once in your life if you can.
A lot of emphasis is put on the personal jihad. Basically, be truthful, friendly, keep your word, avoid hypocrisy, do not steal, do not have sex with women you are not married to, do not do usury, make sure justice is respected. Most Quran teachings are towards controlling each one ego.
Concerning what we call jihad in medias, this is mandatory for all muslims if a non-Muslim army invade a Muslim territory or a group of Muslims is made prisoner by non-Muslims. In this case, it is mandatory to take arms and fight. There are rules of war I will develop in a second post. It is forbidden to fight somebody to convert him.